diff --git a/components/script/dom/cssfontfacerule.rs b/components/script/dom/cssfontfacerule.rs
new file mode 100644
index 00000000000..88dcaf4603f
--- /dev/null
+++ b/components/script/dom/cssfontfacerule.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSFontFaceRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::cssrule::{CSSRule, SpecificCSSRule};
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use parking_lot::RwLock;
+use std::sync::Arc;
+use style::font_face::FontFaceRule;
+
+#[dom_struct]
+pub struct CSSFontFaceRule {
+    cssrule: CSSRule,
+    #[ignore_heap_size_of = "Arc"]
+    fontfacerule: Arc<RwLock<FontFaceRule>>,
+}
+
+impl CSSFontFaceRule {
+    fn new_inherited(parent: &CSSStyleSheet, fontfacerule: Arc<RwLock<FontFaceRule>>) -> CSSFontFaceRule {
+        CSSFontFaceRule {
+            cssrule: CSSRule::new_inherited(parent),
+            fontfacerule: fontfacerule,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet,
+               fontfacerule: Arc<RwLock<FontFaceRule>>) -> Root<CSSFontFaceRule> {
+        reflect_dom_object(box CSSFontFaceRule::new_inherited(parent, fontfacerule),
+                           window,
+                           CSSFontFaceRuleBinding::Wrap)
+    }
+}
+
+impl SpecificCSSRule for CSSFontFaceRule {
+    fn ty(&self) -> u16 {
+        use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
+        CSSRuleConstants::FONT_FACE_RULE
+    }
+
+    fn get_css(&self) -> DOMString {
+        // self.fontfacerule.read().to_css_string().into()
+        "".into()
+    }
+}
diff --git a/components/script/dom/cssgroupingrule.rs b/components/script/dom/cssgroupingrule.rs
new file mode 100644
index 00000000000..3558686ea74
--- /dev/null
+++ b/components/script/dom/cssgroupingrule.rs
@@ -0,0 +1,30 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSGroupingRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::cssrule::CSSRule;
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+
+#[dom_struct]
+pub struct CSSGroupingRule {
+    cssrule: CSSRule,
+}
+
+impl CSSGroupingRule {
+    pub fn new_inherited(parent: &CSSStyleSheet) -> CSSGroupingRule {
+        CSSGroupingRule {
+            cssrule: CSSRule::new_inherited(parent),
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet) -> Root<CSSGroupingRule> {
+        reflect_dom_object(box CSSGroupingRule::new_inherited(parent),
+                           window,
+                           CSSGroupingRuleBinding::Wrap)
+    }
+}
diff --git a/components/script/dom/csskeyframesrule.rs b/components/script/dom/csskeyframesrule.rs
new file mode 100644
index 00000000000..3fced7751d6
--- /dev/null
+++ b/components/script/dom/csskeyframesrule.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSKeyframesRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::cssrule::{CSSRule, SpecificCSSRule};
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use parking_lot::RwLock;
+use std::sync::Arc;
+use style::stylesheets::KeyframesRule;
+
+#[dom_struct]
+pub struct CSSKeyframesRule {
+    cssrule: CSSRule,
+    #[ignore_heap_size_of = "Arc"]
+    keyframesrule: Arc<RwLock<KeyframesRule>>,
+}
+
+impl CSSKeyframesRule {
+    fn new_inherited(parent: &CSSStyleSheet, keyframesrule: Arc<RwLock<KeyframesRule>>) -> CSSKeyframesRule {
+        CSSKeyframesRule {
+            cssrule: CSSRule::new_inherited(parent),
+            keyframesrule: keyframesrule,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet,
+               keyframesrule: Arc<RwLock<KeyframesRule>>) -> Root<CSSKeyframesRule> {
+        reflect_dom_object(box CSSKeyframesRule::new_inherited(parent, keyframesrule),
+                           window,
+                           CSSKeyframesRuleBinding::Wrap)
+    }
+}
+
+impl SpecificCSSRule for CSSKeyframesRule {
+    fn ty(&self) -> u16 {
+        use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
+        CSSRuleConstants::KEYFRAMES_RULE
+    }
+
+    fn get_css(&self) -> DOMString {
+        // self.keyframesrule.read().to_css_string().into()
+        "".into()
+    }
+}
diff --git a/components/script/dom/cssmediarule.rs b/components/script/dom/cssmediarule.rs
new file mode 100644
index 00000000000..dc4f3e586ba
--- /dev/null
+++ b/components/script/dom/cssmediarule.rs
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSMediaRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::cssgroupingrule::CSSGroupingRule;
+use dom::cssrule::SpecificCSSRule;
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use parking_lot::RwLock;
+use std::sync::Arc;
+use style::stylesheets::MediaRule;
+
+#[dom_struct]
+pub struct CSSMediaRule {
+    cssrule: CSSGroupingRule,
+    #[ignore_heap_size_of = "Arc"]
+    mediarule: Arc<RwLock<MediaRule>>,
+}
+
+impl CSSMediaRule {
+    fn new_inherited(parent: &CSSStyleSheet, mediarule: Arc<RwLock<MediaRule>>) -> CSSMediaRule {
+        CSSMediaRule {
+            cssrule: CSSGroupingRule::new_inherited(parent),
+            mediarule: mediarule,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet,
+               mediarule: Arc<RwLock<MediaRule>>) -> Root<CSSMediaRule> {
+        reflect_dom_object(box CSSMediaRule::new_inherited(parent, mediarule),
+                           window,
+                           CSSMediaRuleBinding::Wrap)
+    }
+}
+
+impl SpecificCSSRule for CSSMediaRule {
+    fn ty(&self) -> u16 {
+        use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
+        CSSRuleConstants::MEDIA_RULE
+    }
+
+    fn get_css(&self) -> DOMString {
+        // self.mediarule.read().to_css_string().into()
+        "".into()
+    }
+}
diff --git a/components/script/dom/cssnamespacerule.rs b/components/script/dom/cssnamespacerule.rs
new file mode 100644
index 00000000000..2c0866c5dbe
--- /dev/null
+++ b/components/script/dom/cssnamespacerule.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSNamespaceRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::cssrule::{CSSRule, SpecificCSSRule};
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use parking_lot::RwLock;
+use std::sync::Arc;
+use style::stylesheets::NamespaceRule;
+
+#[dom_struct]
+pub struct CSSNamespaceRule {
+    cssrule: CSSRule,
+    #[ignore_heap_size_of = "Arc"]
+    namespacerule: Arc<RwLock<NamespaceRule>>,
+}
+
+impl CSSNamespaceRule {
+    fn new_inherited(parent: &CSSStyleSheet, namespacerule: Arc<RwLock<NamespaceRule>>) -> CSSNamespaceRule {
+        CSSNamespaceRule {
+            cssrule: CSSRule::new_inherited(parent),
+            namespacerule: namespacerule,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet,
+               namespacerule: Arc<RwLock<NamespaceRule>>) -> Root<CSSNamespaceRule> {
+        reflect_dom_object(box CSSNamespaceRule::new_inherited(parent, namespacerule),
+                           window,
+                           CSSNamespaceRuleBinding::Wrap)
+    }
+}
+
+impl SpecificCSSRule for CSSNamespaceRule {
+    fn ty(&self) -> u16 {
+        use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
+        CSSRuleConstants::NAMESPACE_RULE
+    }
+
+    fn get_css(&self) -> DOMString {
+        // self.namespacerule.read().to_css_string().into()
+        "".into()
+    }
+}
diff --git a/components/script/dom/cssrule.rs b/components/script/dom/cssrule.rs
new file mode 100644
index 00000000000..e46738bb1b4
--- /dev/null
+++ b/components/script/dom/cssrule.rs
@@ -0,0 +1,103 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSRuleBinding;
+use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleMethods;
+use dom::bindings::inheritance::Castable;
+use dom::bindings::js::{JS, MutNullableHeap, Root};
+use dom::bindings::reflector::{Reflector, reflect_dom_object};
+use dom::bindings::str::DOMString;
+use dom::cssfontfacerule::CSSFontFaceRule;
+use dom::csskeyframesrule::CSSKeyframesRule;
+use dom::cssmediarule::CSSMediaRule;
+use dom::cssnamespacerule::CSSNamespaceRule;
+use dom::cssstylerule::CSSStyleRule;
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::cssviewportrule::CSSViewportRule;
+use dom::window::Window;
+use style::stylesheets::CssRule as StyleCssRule;
+
+
+#[dom_struct]
+pub struct CSSRule {
+    reflector_: Reflector,
+    parent: MutNullableHeap<JS<CSSStyleSheet>>,
+}
+
+impl CSSRule {
+    #[allow(unrooted_must_root)]
+    pub fn new_inherited(parent: &CSSStyleSheet) -> CSSRule {
+        CSSRule {
+            reflector_: Reflector::new(),
+            parent: MutNullableHeap::new(Some(parent)),
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet) -> Root<CSSRule> {
+        reflect_dom_object(box CSSRule::new_inherited(parent),
+                           window,
+                           CSSRuleBinding::Wrap)
+    }
+
+    pub fn as_specific(&self) -> &SpecificCSSRule {
+        if let Some(rule) = self.downcast::<CSSStyleRule>() {
+            rule as &SpecificCSSRule
+        } else if let Some(rule) = self.downcast::<CSSFontFaceRule>() {
+            rule as &SpecificCSSRule
+        } else if let Some(rule) = self.downcast::<CSSKeyframesRule>() {
+            rule as &SpecificCSSRule
+        } else if let Some(rule) = self.downcast::<CSSMediaRule>() {
+            rule as &SpecificCSSRule
+        } else if let Some(rule) = self.downcast::<CSSNamespaceRule>() {
+            rule as &SpecificCSSRule
+        } else if let Some(rule) = self.downcast::<CSSViewportRule>() {
+            rule as &SpecificCSSRule
+        } else {
+            unreachable!()
+        }
+    }
+
+    // Given a StyleCssRule, create a new instance of a derived class of
+    // CSSRule based on which rule it is
+    pub fn new_specific(window: &Window, parent: &CSSStyleSheet,
+                        rule: StyleCssRule) -> Root<CSSRule> {
+        // be sure to update the match in as_specific when this is updated
+        match rule {
+            StyleCssRule::Style(s) => Root::upcast(CSSStyleRule::new(window, parent, s)),
+            StyleCssRule::FontFace(s) => Root::upcast(CSSFontFaceRule::new(window, parent, s)),
+            StyleCssRule::Keyframes(s) => Root::upcast(CSSKeyframesRule::new(window, parent, s)),
+            StyleCssRule::Media(s) => Root::upcast(CSSMediaRule::new(window, parent, s)),
+            StyleCssRule::Namespace(s) => Root::upcast(CSSNamespaceRule::new(window, parent, s)),
+            StyleCssRule::Viewport(s) => Root::upcast(CSSViewportRule::new(window, parent, s)),
+        }
+    }
+}
+
+impl CSSRuleMethods for CSSRule {
+    // https://drafts.csswg.org/cssom/#dom-cssrule-type
+    fn Type(&self) -> u16 {
+        self.as_specific().ty()
+    }
+
+    // https://drafts.csswg.org/cssom/#dom-cssrule-parentstylesheet
+    fn GetParentStyleSheet(&self) -> Option<Root<CSSStyleSheet>> {
+        self.parent.get()
+    }
+
+    // https://drafts.csswg.org/cssom/#dom-cssrule-csstext
+    fn CssText(&self) -> DOMString {
+        self.as_specific().get_css()
+    }
+
+    // https://drafts.csswg.org/cssom/#dom-cssrule-csstext
+    fn SetCssText(&self, _: DOMString) {
+        // do nothing
+    }
+}
+
+pub trait SpecificCSSRule {
+    fn ty(&self) -> u16;
+    fn get_css(&self) -> DOMString;
+}
diff --git a/components/script/dom/cssrulelist.rs b/components/script/dom/cssrulelist.rs
new file mode 100644
index 00000000000..1c383403a00
--- /dev/null
+++ b/components/script/dom/cssrulelist.rs
@@ -0,0 +1,67 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSRuleListBinding;
+use dom::bindings::codegen::Bindings::CSSRuleListBinding::CSSRuleListMethods;
+use dom::bindings::js::{JS, MutNullableHeap, Root};
+use dom::bindings::reflector::{Reflectable, Reflector, reflect_dom_object};
+use dom::cssrule::CSSRule;
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use style::stylesheets::CssRules;
+
+no_jsmanaged_fields!(CssRules);
+
+#[dom_struct]
+pub struct CSSRuleList {
+    reflector_: Reflector,
+    sheet: JS<CSSStyleSheet>,
+    #[ignore_heap_size_of = "Arc"]
+    rules: CssRules,
+    dom_rules: Vec<MutNullableHeap<JS<CSSRule>>>
+}
+
+impl CSSRuleList {
+    #[allow(unrooted_must_root)]
+    pub fn new_inherited(sheet: &CSSStyleSheet, rules: CssRules) -> CSSRuleList {
+        let dom_rules = rules.0.read().iter().map(|_| MutNullableHeap::new(None)).collect();
+        CSSRuleList {
+            reflector_: Reflector::new(),
+            sheet: JS::from_ref(sheet),
+            rules: rules,
+            dom_rules: dom_rules,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, sheet: &CSSStyleSheet, rules: CssRules) -> Root<CSSRuleList> {
+        reflect_dom_object(box CSSRuleList::new_inherited(sheet, rules),
+                           window,
+                           CSSRuleListBinding::Wrap)
+    }
+}
+
+impl CSSRuleListMethods for CSSRuleList {
+    // https://drafts.csswg.org/cssom/#ref-for-dom-cssrulelist-item-1
+    fn Item(&self, idx: u32) -> Option<Root<CSSRule>> {
+        self.dom_rules.get(idx as usize).map(|rule| {
+            rule.or_init(|| {
+                CSSRule::new_specific(self.global().as_window(),
+                                     &self.sheet,
+                                     self.rules.0.read()[idx as usize].clone())
+            })
+        })
+    }
+
+    // https://drafts.csswg.org/cssom/#dom-cssrulelist-length
+    fn Length(&self) -> u32 {
+        self.dom_rules.len() as u32
+    }
+
+    // check-tidy: no specs after this line
+    fn IndexedGetter(&self, index: u32) -> Option<Root<CSSRule>> {
+        self.Item(index)
+    }
+}
+
diff --git a/components/script/dom/cssstylerule.rs b/components/script/dom/cssstylerule.rs
new file mode 100644
index 00000000000..30726018ca9
--- /dev/null
+++ b/components/script/dom/cssstylerule.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSStyleRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::cssrule::{CSSRule, SpecificCSSRule};
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use parking_lot::RwLock;
+use std::sync::Arc;
+use style::stylesheets::StyleRule;
+use style_traits::ToCss;
+
+#[dom_struct]
+pub struct CSSStyleRule {
+    cssrule: CSSRule,
+    #[ignore_heap_size_of = "Arc"]
+    stylerule: Arc<RwLock<StyleRule>>,
+}
+
+impl CSSStyleRule {
+    fn new_inherited(parent: &CSSStyleSheet, stylerule: Arc<RwLock<StyleRule>>) -> CSSStyleRule {
+        CSSStyleRule {
+            cssrule: CSSRule::new_inherited(parent),
+            stylerule: stylerule,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet,
+               stylerule: Arc<RwLock<StyleRule>>) -> Root<CSSStyleRule> {
+        reflect_dom_object(box CSSStyleRule::new_inherited(parent, stylerule),
+                           window,
+                           CSSStyleRuleBinding::Wrap)
+    }
+}
+
+impl SpecificCSSRule for CSSStyleRule {
+    fn ty(&self) -> u16 {
+        use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
+        CSSRuleConstants::STYLE_RULE
+    }
+
+    fn get_css(&self) -> DOMString {
+        self.stylerule.read().to_css_string().into()
+    }
+}
diff --git a/components/script/dom/cssstylesheet.rs b/components/script/dom/cssstylesheet.rs
new file mode 100644
index 00000000000..d5a9342a75a
--- /dev/null
+++ b/components/script/dom/cssstylesheet.rs
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSStyleSheetBinding;
+use dom::bindings::codegen::Bindings::CSSStyleSheetBinding::CSSStyleSheetMethods;
+use dom::bindings::js::{JS, Root, MutNullableHeap};
+use dom::bindings::reflector::{reflect_dom_object, Reflectable};
+use dom::bindings::str::DOMString;
+use dom::cssrulelist::CSSRuleList;
+use dom::stylesheet::StyleSheet;
+use dom::window::Window;
+use std::sync::Arc;
+use style::stylesheets::Stylesheet as StyleStyleSheet;
+
+#[dom_struct]
+pub struct CSSStyleSheet {
+    stylesheet: StyleSheet,
+    rulelist: MutNullableHeap<JS<CSSRuleList>>,
+    #[ignore_heap_size_of = "Arc"]
+    style_stylesheet: Arc<StyleStyleSheet>,
+}
+
+impl CSSStyleSheet {
+    fn new_inherited(type_: DOMString, href: Option<DOMString>,
+                     title: Option<DOMString>, stylesheet: Arc<StyleStyleSheet>) -> CSSStyleSheet {
+        CSSStyleSheet {
+            stylesheet: StyleSheet::new_inherited(type_, href, title),
+            rulelist: MutNullableHeap::new(None),
+            style_stylesheet: stylesheet,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, type_: DOMString,
+               href: Option<DOMString>,
+               title: Option<DOMString>,
+               stylesheet: Arc<StyleStyleSheet>) -> Root<CSSStyleSheet> {
+        reflect_dom_object(box CSSStyleSheet::new_inherited(type_, href, title, stylesheet),
+                           window,
+                           CSSStyleSheetBinding::Wrap)
+    }
+}
+
+impl CSSStyleSheetMethods for CSSStyleSheet {
+    // https://drafts.csswg.org/cssom/#dom-cssstylesheet-cssrules
+    fn CssRules(&self) -> Root<CSSRuleList> {
+        self.rulelist.or_init(|| CSSRuleList::new(self.global().as_window(), self, self.style_stylesheet.rules.clone()))
+    }
+}
+
diff --git a/components/script/dom/cssviewportrule.rs b/components/script/dom/cssviewportrule.rs
new file mode 100644
index 00000000000..89f1ada597d
--- /dev/null
+++ b/components/script/dom/cssviewportrule.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::codegen::Bindings::CSSViewportRuleBinding;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::cssrule::{CSSRule, SpecificCSSRule};
+use dom::cssstylesheet::CSSStyleSheet;
+use dom::window::Window;
+use parking_lot::RwLock;
+use std::sync::Arc;
+use style::viewport::ViewportRule;
+
+#[dom_struct]
+pub struct CSSViewportRule {
+    cssrule: CSSRule,
+    #[ignore_heap_size_of = "Arc"]
+    viewportrule: Arc<RwLock<ViewportRule>>,
+}
+
+impl CSSViewportRule {
+    fn new_inherited(parent: &CSSStyleSheet, viewportrule: Arc<RwLock<ViewportRule>>) -> CSSViewportRule {
+        CSSViewportRule {
+            cssrule: CSSRule::new_inherited(parent),
+            viewportrule: viewportrule,
+        }
+    }
+
+    #[allow(unrooted_must_root)]
+    pub fn new(window: &Window, parent: &CSSStyleSheet,
+               viewportrule: Arc<RwLock<ViewportRule>>) -> Root<CSSViewportRule> {
+        reflect_dom_object(box CSSViewportRule::new_inherited(parent, viewportrule),
+                           window,
+                           CSSViewportRuleBinding::Wrap)
+    }
+}
+
+impl SpecificCSSRule for CSSViewportRule {
+    fn ty(&self) -> u16 {
+        use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
+        CSSRuleConstants::VIEWPORT_RULE
+    }
+
+    fn get_css(&self) -> DOMString {
+        // self.viewportrule.read().to_css_string().into()
+        "".into()
+    }
+}
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 5b1f4cfe404..56b7b17b0ca 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -59,10 +59,7 @@ use dom::htmlheadelement::HTMLHeadElement;
 use dom::htmlhtmlelement::HTMLHtmlElement;
 use dom::htmliframeelement::HTMLIFrameElement;
 use dom::htmlimageelement::HTMLImageElement;
-use dom::htmllinkelement::HTMLLinkElement;
-use dom::htmlmetaelement::HTMLMetaElement;
 use dom::htmlscriptelement::HTMLScriptElement;
-use dom::htmlstyleelement::HTMLStyleElement;
 use dom::htmltitleelement::HTMLTitleElement;
 use dom::keyboardevent::KeyboardEvent;
 use dom::location::Location;
@@ -152,10 +149,10 @@ enum ParserBlockedByScript {
 
 #[derive(JSTraceable, HeapSizeOf)]
 #[must_root]
-struct StylesheetInDocument {
-    node: JS<Node>,
+pub struct StylesheetInDocument {
+    pub node: JS<Node>,
     #[ignore_heap_size_of = "Arc"]
-    stylesheet: Arc<Stylesheet>,
+    pub stylesheet: Arc<Stylesheet>,
 }
 
 // https://dom.spec.whatwg.org/#document
@@ -189,6 +186,7 @@ pub struct Document {
     stylesheets: DOMRefCell<Option<Vec<StylesheetInDocument>>>,
     /// Whether the list of stylesheets has changed since the last reflow was triggered.
     stylesheets_changed_since_reflow: Cell<bool>,
+    stylesheet_list: MutNullableHeap<JS<StyleSheetList>>,
     ready_state: Cell<DocumentReadyState>,
     /// Whether the DOMContentLoaded event has already been dispatched.
     domcontentloaded_dispatched: Cell<bool>,
@@ -1811,6 +1809,7 @@ impl Document {
             applets: Default::default(),
             stylesheets: DOMRefCell::new(None),
             stylesheets_changed_since_reflow: Cell::new(false),
+            stylesheet_list: MutNullableHeap::new(None),
             ready_state: Cell::new(ready_state),
             domcontentloaded_dispatched: Cell::new(domcontentloaded_dispatched),
             possibly_focused: Default::default(),
@@ -1910,35 +1909,37 @@ impl Document {
         self.GetDocumentElement().and_then(Root::downcast)
     }
 
+    // Ensure that the stylesheets vector is populated
+    fn ensure_stylesheets(&self) {
+        let mut stylesheets = self.stylesheets.borrow_mut();
+        if stylesheets.is_none() {
+            *stylesheets = Some(self.upcast::<Node>()
+                .traverse_preorder()
+                .filter_map(|node| {
+                    node.get_stylesheet()
+                        .map(|stylesheet| StylesheetInDocument {
+                        node: JS::from_ref(&*node),
+                        stylesheet: stylesheet,
+                    })
+                })
+                .collect());
+        };
+    }
+
     /// Returns the list of stylesheets associated with nodes in the document.
     pub fn stylesheets(&self) -> Vec<Arc<Stylesheet>> {
-        {
-            let mut stylesheets = self.stylesheets.borrow_mut();
-            if stylesheets.is_none() {
-                *stylesheets = Some(self.upcast::<Node>()
-                    .traverse_preorder()
-                    .filter_map(|node| {
-                        if let Some(node) = node.downcast::<HTMLStyleElement>() {
-                            node.get_stylesheet()
-                        } else if let Some(node) = node.downcast::<HTMLLinkElement>() {
-                            node.get_stylesheet()
-                        } else if let Some(node) = node.downcast::<HTMLMetaElement>() {
-                            node.get_stylesheet()
-                        } else {
-                            None
-                        }.map(|stylesheet| StylesheetInDocument {
-                            node: JS::from_ref(&*node),
-                            stylesheet: stylesheet
-                        })
-                    })
-                    .collect());
-            };
-        }
+        self.ensure_stylesheets();
         self.stylesheets.borrow().as_ref().unwrap().iter()
                         .map(|s| s.stylesheet.clone())
                         .collect()
     }
 
+    pub fn with_style_sheets_in_document<F, T>(&self, mut f: F) -> T
+            where F: FnMut(&[StylesheetInDocument]) -> T {
+        self.ensure_stylesheets();
+        f(&self.stylesheets.borrow().as_ref().unwrap())
+    }
+
     /// https://html.spec.whatwg.org/multipage/#appropriate-template-contents-owner-document
     pub fn appropriate_template_contents_owner_document(&self) -> Root<Document> {
         self.appropriate_template_contents_owner_document.or_init(|| {
@@ -2038,7 +2039,7 @@ impl Element {
 impl DocumentMethods for Document {
     // https://drafts.csswg.org/cssom/#dom-document-stylesheets
     fn StyleSheets(&self) -> Root<StyleSheetList> {
-        StyleSheetList::new(&self.window, JS::from_ref(&self))
+        self.stylesheet_list.or_init(|| StyleSheetList::new(&self.window, JS::from_ref(&self)))
     }
 
     // https://dom.spec.whatwg.org/#dom-document-implementation
diff --git a/components/script/dom/htmllinkelement.rs b/components/script/dom/htmllinkelement.rs
index 5df64f62ca0..17c9514287e 100644
--- a/components/script/dom/htmllinkelement.rs
+++ b/components/script/dom/htmllinkelement.rs
@@ -14,6 +14,7 @@ use dom::bindings::js::{JS, MutNullableHeap, Root, RootedReference};
 use dom::bindings::refcounted::Trusted;
 use dom::bindings::reflector::Reflectable;
 use dom::bindings::str::DOMString;
+use dom::cssstylesheet::CSSStyleSheet;
 use dom::document::Document;
 use dom::domtokenlist::DOMTokenList;
 use dom::element::{AttributeMutation, Element, ElementCreator};
@@ -56,6 +57,7 @@ pub struct HTMLLinkElement {
     rel_list: MutNullableHeap<JS<DOMTokenList>>,
     #[ignore_heap_size_of = "Arc"]
     stylesheet: DOMRefCell<Option<Arc<Stylesheet>>>,
+    cssom_stylesheet: MutNullableHeap<JS<CSSStyleSheet>>,
 
     /// https://html.spec.whatwg.org/multipage/#a-style-sheet-that-is-blocking-scripts
     parser_inserted: Cell<bool>,
@@ -69,6 +71,7 @@ impl HTMLLinkElement {
             rel_list: Default::default(),
             parser_inserted: Cell::new(creator == ElementCreator::ParserCreated),
             stylesheet: DOMRefCell::new(None),
+            cssom_stylesheet: MutNullableHeap::new(None),
         }
     }
 
@@ -85,6 +88,18 @@ impl HTMLLinkElement {
     pub fn get_stylesheet(&self) -> Option<Arc<Stylesheet>> {
         self.stylesheet.borrow().clone()
     }
+
+    pub fn get_cssom_stylesheet(&self) -> Option<Root<CSSStyleSheet>> {
+        self.get_stylesheet().map(|sheet| {
+            self.cssom_stylesheet.or_init(|| {
+                CSSStyleSheet::new(&window_from_node(self),
+                                   "text/css".into(),
+                                   None, // todo handle location
+                                   None, // todo handle title
+                                   sheet)
+            })
+        })
+    }
 }
 
 fn get_attr(element: &Element, local_name: &LocalName) -> Option<String> {
diff --git a/components/script/dom/htmlmetaelement.rs b/components/script/dom/htmlmetaelement.rs
index 82855472589..c948dde4ab8 100644
--- a/components/script/dom/htmlmetaelement.rs
+++ b/components/script/dom/htmlmetaelement.rs
@@ -8,13 +8,14 @@ use dom::bindings::codegen::Bindings::HTMLMetaElementBinding;
 use dom::bindings::codegen::Bindings::HTMLMetaElementBinding::HTMLMetaElementMethods;
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use dom::bindings::inheritance::Castable;
-use dom::bindings::js::{Root, RootedReference};
+use dom::bindings::js::{JS, MutNullableHeap, Root, RootedReference};
 use dom::bindings::str::DOMString;
+use dom::cssstylesheet::CSSStyleSheet;
 use dom::document::Document;
 use dom::element::{AttributeMutation, Element};
 use dom::htmlelement::HTMLElement;
 use dom::htmlheadelement::HTMLHeadElement;
-use dom::node::{Node, UnbindContext, document_from_node};
+use dom::node::{Node, UnbindContext, document_from_node, window_from_node};
 use dom::virtualmethods::VirtualMethods;
 use html5ever_atoms::LocalName;
 use parking_lot::RwLock;
@@ -30,6 +31,7 @@ pub struct HTMLMetaElement {
     htmlelement: HTMLElement,
     #[ignore_heap_size_of = "Arc"]
     stylesheet: DOMRefCell<Option<Arc<Stylesheet>>>,
+    cssom_stylesheet: MutNullableHeap<JS<CSSStyleSheet>>,
 }
 
 impl HTMLMetaElement {
@@ -39,6 +41,7 @@ impl HTMLMetaElement {
         HTMLMetaElement {
             htmlelement: HTMLElement::new_inherited(local_name, prefix, document),
             stylesheet: DOMRefCell::new(None),
+            cssom_stylesheet: MutNullableHeap::new(None),
         }
     }
 
@@ -55,6 +58,18 @@ impl HTMLMetaElement {
         self.stylesheet.borrow().clone()
     }
 
+    pub fn get_cssom_stylesheet(&self) -> Option<Root<CSSStyleSheet>> {
+        self.get_stylesheet().map(|sheet| {
+            self.cssom_stylesheet.or_init(|| {
+                CSSStyleSheet::new(&window_from_node(self),
+                                   "text/css".into(),
+                                   None, // todo handle location
+                                   None, // todo handle title
+                                   sheet)
+            })
+        })
+    }
+
     fn process_attributes(&self) {
         let element = self.upcast::<Element>();
         if let Some(name) = element.get_attribute(&ns!(), &local_name!("name")).r() {
@@ -81,7 +96,7 @@ impl HTMLMetaElement {
             if !content.is_empty() {
                 if let Some(translated_rule) = ViewportRule::from_meta(&**content) {
                     *self.stylesheet.borrow_mut() = Some(Arc::new(Stylesheet {
-                        rules: vec![CssRule::Viewport(Arc::new(RwLock::new(translated_rule)))],
+                        rules: vec![CssRule::Viewport(Arc::new(RwLock::new(translated_rule)))].into(),
                         origin: Origin::Author,
                         media: Default::default(),
                         // Viewport constraints are always recomputed on resize; they don't need to
diff --git a/components/script/dom/htmlstyleelement.rs b/components/script/dom/htmlstyleelement.rs
index 8c1bc031dc0..577e290a3ea 100644
--- a/components/script/dom/htmlstyleelement.rs
+++ b/components/script/dom/htmlstyleelement.rs
@@ -7,8 +7,9 @@ use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::HTMLStyleElementBinding;
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use dom::bindings::inheritance::Castable;
-use dom::bindings::js::Root;
+use dom::bindings::js::{JS, MutNullableHeap, Root};
 use dom::bindings::str::DOMString;
+use dom::cssstylesheet::CSSStyleSheet;
 use dom::document::Document;
 use dom::element::Element;
 use dom::htmlelement::HTMLElement;
@@ -26,6 +27,7 @@ pub struct HTMLStyleElement {
     htmlelement: HTMLElement,
     #[ignore_heap_size_of = "Arc"]
     stylesheet: DOMRefCell<Option<Arc<Stylesheet>>>,
+    cssom_stylesheet: MutNullableHeap<JS<CSSStyleSheet>>,
 }
 
 impl HTMLStyleElement {
@@ -35,6 +37,7 @@ impl HTMLStyleElement {
         HTMLStyleElement {
             htmlelement: HTMLElement::new_inherited(local_name, prefix, document),
             stylesheet: DOMRefCell::new(None),
+            cssom_stylesheet: MutNullableHeap::new(None),
         }
     }
 
@@ -77,6 +80,18 @@ impl HTMLStyleElement {
     pub fn get_stylesheet(&self) -> Option<Arc<Stylesheet>> {
         self.stylesheet.borrow().clone()
     }
+
+    pub fn get_cssom_stylesheet(&self) -> Option<Root<CSSStyleSheet>> {
+        self.get_stylesheet().map(|sheet| {
+            self.cssom_stylesheet.or_init(|| {
+                CSSStyleSheet::new(&window_from_node(self),
+                                   "text/css".into(),
+                                   None, // todo handle location
+                                   None, // todo handle title
+                                   sheet)
+            })
+        })
+    }
 }
 
 impl VirtualMethods for HTMLStyleElement {
diff --git a/components/script/dom/mod.rs b/components/script/dom/mod.rs
index d419d41ec61..05ec1963a20 100644
--- a/components/script/dom/mod.rs
+++ b/components/script/dom/mod.rs
@@ -242,7 +242,17 @@ pub mod comment;
 pub mod console;
 pub mod crypto;
 pub mod css;
+pub mod cssfontfacerule;
+pub mod cssgroupingrule;
+pub mod csskeyframesrule;
+pub mod cssmediarule;
+pub mod cssnamespacerule;
+pub mod cssrule;
+pub mod cssrulelist;
 pub mod cssstyledeclaration;
+pub mod cssstylerule;
+pub mod cssstylesheet;
+pub mod cssviewportrule;
 pub mod customevent;
 pub mod dedicatedworkerglobalscope;
 pub mod document;
diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 0f510719640..37e0548fa13 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -30,6 +30,7 @@ use dom::bindings::reflector::{Reflectable, reflect_dom_object};
 use dom::bindings::str::{DOMString, USVString};
 use dom::bindings::xmlname::namespace_from_domstring;
 use dom::characterdata::{CharacterData, LayoutCharacterDataHelpers};
+use dom::cssstylesheet::CSSStyleSheet;
 use dom::document::{Document, DocumentSource, IsHTMLDocument};
 use dom::documentfragment::DocumentFragment;
 use dom::documenttype::DocumentType;
@@ -43,6 +44,9 @@ use dom::htmlelement::HTMLElement;
 use dom::htmliframeelement::{HTMLIFrameElement, HTMLIFrameElementLayoutMethods};
 use dom::htmlimageelement::{HTMLImageElement, LayoutHTMLImageElementHelpers};
 use dom::htmlinputelement::{HTMLInputElement, LayoutHTMLInputElementHelpers};
+use dom::htmllinkelement::HTMLLinkElement;
+use dom::htmlmetaelement::HTMLMetaElement;
+use dom::htmlstyleelement::HTMLStyleElement;
 use dom::htmltextareaelement::{HTMLTextAreaElement, LayoutHTMLTextAreaElementHelpers};
 use dom::nodelist::NodeList;
 use dom::processinginstruction::ProcessingInstruction;
@@ -76,8 +80,10 @@ use std::default::Default;
 use std::iter;
 use std::mem;
 use std::ops::Range;
+use std::sync::Arc;
 use style::dom::OpaqueNode;
 use style::selector_impl::ServoSelectorImpl;
+use style::stylesheets::Stylesheet;
 use style::thread_state;
 use url::Url;
 use uuid::Uuid;
@@ -901,6 +907,30 @@ impl Node {
         element.upcast::<Node>().remove_self();
         Ok(())
     }
+
+    pub fn get_stylesheet(&self) -> Option<Arc<Stylesheet>> {
+        if let Some(node) = self.downcast::<HTMLStyleElement>() {
+            node.get_stylesheet()
+        } else if let Some(node) = self.downcast::<HTMLLinkElement>() {
+            node.get_stylesheet()
+        } else if let Some(node) = self.downcast::<HTMLMetaElement>() {
+            node.get_stylesheet()
+        } else {
+            None
+        }
+    }
+
+    pub fn get_cssom_stylesheet(&self) -> Option<Root<CSSStyleSheet>> {
+        if let Some(node) = self.downcast::<HTMLStyleElement>() {
+            node.get_cssom_stylesheet()
+        } else if let Some(node) = self.downcast::<HTMLLinkElement>() {
+            node.get_cssom_stylesheet()
+        } else if let Some(node) = self.downcast::<HTMLMetaElement>() {
+            node.get_cssom_stylesheet()
+        } else {
+            None
+        }
+    }
 }
 
 
diff --git a/components/script/dom/stylesheet.rs b/components/script/dom/stylesheet.rs
index 02c96623800..7def8f1ba6c 100644
--- a/components/script/dom/stylesheet.rs
+++ b/components/script/dom/stylesheet.rs
@@ -20,7 +20,7 @@ pub struct StyleSheet {
 
 impl StyleSheet {
     #[allow(unrooted_must_root)]
-    fn new_inherited(type_: DOMString, href: Option<DOMString>, title: Option<DOMString>) -> StyleSheet {
+    pub fn new_inherited(type_: DOMString, href: Option<DOMString>, title: Option<DOMString>) -> StyleSheet {
         StyleSheet {
             reflector_: Reflector::new(),
             type_: type_,
diff --git a/components/script/dom/stylesheetlist.rs b/components/script/dom/stylesheetlist.rs
index a4541fc9bb4..b028e7f2b73 100644
--- a/components/script/dom/stylesheetlist.rs
+++ b/components/script/dom/stylesheetlist.rs
@@ -35,13 +35,18 @@ impl StyleSheetList {
 impl StyleSheetListMethods for StyleSheetList {
     // https://drafts.csswg.org/cssom/#dom-stylesheetlist-length
     fn Length(&self) -> u32 {
-       self.document.stylesheets().len() as u32
+       self.document.with_style_sheets_in_document(|s| s.len() as u32)
     }
 
     // https://drafts.csswg.org/cssom/#dom-stylesheetlist-item
-    fn Item(&self, _index: u32) -> Option<Root<StyleSheet>> {
-        None
-        //TODO Create a new StyleSheet object and return it
+    fn Item(&self, index: u32) -> Option<Root<StyleSheet>> {
+        // XXXManishearth this  doesn't handle the origin clean flag
+        // and is a cors vulnerability
+        self.document.with_style_sheets_in_document(|sheets| {
+            sheets.get(index as usize)
+                  .and_then(|sheet| sheet.node.get_cssom_stylesheet())
+                  .map(Root::upcast)
+        })
     }
 
     // check-tidy: no specs after this line
diff --git a/components/script/dom/webidls/CSS.webidl b/components/script/dom/webidls/CSS.webidl
index 54458060909..438c6814ccb 100644
--- a/components/script/dom/webidls/CSS.webidl
+++ b/components/script/dom/webidls/CSS.webidl
@@ -6,7 +6,7 @@
  * http://dev.w3.org/csswg/cssom/#the-css-interface
  */
 
-[Abstract, Exposed=(Window,Worker)]
+[Abstract, Exposed=Window]
 interface CSS {
   [Throws]
   static DOMString escape(DOMString ident);
diff --git a/components/script/dom/webidls/CSSFontFaceRule.webidl b/components/script/dom/webidls/CSSFontFaceRule.webidl
new file mode 100644
index 00000000000..3749a79a818
--- /dev/null
+++ b/components/script/dom/webidls/CSSFontFaceRule.webidl
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/css-fonts/#cssfontfacerule
+[Exposed=Window]
+interface CSSFontFaceRule : CSSRule {
+  // attribute DOMString family;
+  // attribute DOMString src;
+  // attribute DOMString style;
+  // attribute DOMString weight;
+  // attribute DOMString stretch;
+  // attribute DOMString unicodeRange;
+  // attribute DOMString variant;
+  // attribute DOMString featureSettings;
+};
+
diff --git a/components/script/dom/webidls/CSSGroupingRule.webidl b/components/script/dom/webidls/CSSGroupingRule.webidl
new file mode 100644
index 00000000000..6a317191ff6
--- /dev/null
+++ b/components/script/dom/webidls/CSSGroupingRule.webidl
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#the-cssgroupingrule-interface
+[Exposed=Window]
+interface CSSGroupingRule : CSSRule {
+  // [SameObject] readonly attribute CSSRuleList cssRules;
+  // unsigned long insertRule(DOMString rule, unsigned long index);
+  // void deleteRule(unsigned long index);
+};
+
diff --git a/components/script/dom/webidls/CSSKeyframesRule.webidl b/components/script/dom/webidls/CSSKeyframesRule.webidl
new file mode 100644
index 00000000000..db152d72850
--- /dev/null
+++ b/components/script/dom/webidls/CSSKeyframesRule.webidl
@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/css-animations/#interface-csskeyframesrule
+[Exposed=Window]
+interface CSSKeyframesRule : CSSRule {
+  //          attribute DOMString   name;
+  // readonly attribute CSSRuleList cssRules;
+
+  // void            appendRule(DOMString rule);
+  // void            deleteRule(DOMString select);
+  // CSSKeyframeRule? findRule(DOMString select);
+};
diff --git a/components/script/dom/webidls/CSSMediaRule.webidl b/components/script/dom/webidls/CSSMediaRule.webidl
new file mode 100644
index 00000000000..e2b89dee723
--- /dev/null
+++ b/components/script/dom/webidls/CSSMediaRule.webidl
@@ -0,0 +1,9 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#the-cssmediarule-interface
+[Exposed=Window]
+interface CSSMediaRule : CSSGroupingRule {
+  // [SameObject, PutForwards=mediaText] readonly attribute MediaList media;
+};
diff --git a/components/script/dom/webidls/CSSNamespaceRule.webidl b/components/script/dom/webidls/CSSNamespaceRule.webidl
new file mode 100644
index 00000000000..a8d6b61548f
--- /dev/null
+++ b/components/script/dom/webidls/CSSNamespaceRule.webidl
@@ -0,0 +1,10 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#the-cssnamespacerule-interface
+[Exposed=Window]
+interface CSSNamespaceRule : CSSRule {
+  // readonly attribute DOMString namespaceURI;
+  // readonly attribute DOMString prefix;
+};
diff --git a/components/script/dom/webidls/CSSRule.webidl b/components/script/dom/webidls/CSSRule.webidl
new file mode 100644
index 00000000000..462943430e6
--- /dev/null
+++ b/components/script/dom/webidls/CSSRule.webidl
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#the-cssrule-interface
+[Exposed=Window]
+interface CSSRule {
+  const unsigned short STYLE_RULE = 1;
+  const unsigned short CHARSET_RULE = 2; // historical
+  const unsigned short IMPORT_RULE = 3;
+  const unsigned short MEDIA_RULE = 4;
+  const unsigned short FONT_FACE_RULE = 5;
+  const unsigned short PAGE_RULE = 6;
+  const unsigned short MARGIN_RULE = 9;
+  const unsigned short NAMESPACE_RULE = 10;
+
+  readonly attribute unsigned short type;
+  attribute DOMString cssText;
+  // readonly attribute CSSRule? parentRule;
+  readonly attribute CSSStyleSheet? parentStyleSheet;
+};
+
+// https://drafts.csswg.org/css-animations/#interface-cssrule-idl
+partial interface CSSRule {
+    const unsigned short KEYFRAMES_RULE = 7;
+    const unsigned short KEYFRAME_RULE = 8;
+};
+
+// https://drafts.csswg.org/css-device-adapt/#css-rule-interface
+partial interface CSSRule {
+    const unsigned short VIEWPORT_RULE = 15;
+};
+
diff --git a/components/script/dom/webidls/CSSRuleList.webidl b/components/script/dom/webidls/CSSRuleList.webidl
new file mode 100644
index 00000000000..8ee12004a26
--- /dev/null
+++ b/components/script/dom/webidls/CSSRuleList.webidl
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#cssrulelist
+// [LegacyArrayClass]
+[Exposed=Window]
+interface CSSRuleList {
+  getter CSSRule? item(unsigned long index);
+  readonly attribute unsigned long length;
+};
diff --git a/components/script/dom/webidls/CSSStyleDeclaration.webidl b/components/script/dom/webidls/CSSStyleDeclaration.webidl
index 3424e5593a6..0f0b483d0b1 100644
--- a/components/script/dom/webidls/CSSStyleDeclaration.webidl
+++ b/components/script/dom/webidls/CSSStyleDeclaration.webidl
@@ -8,7 +8,7 @@
  * Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved.
  */
 
-[Exposed=(Window,Worker)]
+[Exposed=(Window, Worker)]
 interface CSSStyleDeclaration {
   [SetterThrows]
            attribute DOMString cssText;
diff --git a/components/script/dom/webidls/CSSStyleRule.webidl b/components/script/dom/webidls/CSSStyleRule.webidl
new file mode 100644
index 00000000000..faee525e7ff
--- /dev/null
+++ b/components/script/dom/webidls/CSSStyleRule.webidl
@@ -0,0 +1,10 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#the-cssstylerule-interface
+[Exposed=Window]
+interface CSSStyleRule : CSSRule {
+  // attribute DOMString selectorText;
+  // [SameObject, PutForwards=cssText] readonly attribute CSSStyleDeclaration style;
+};
diff --git a/components/script/dom/webidls/CSSStyleSheet.webidl b/components/script/dom/webidls/CSSStyleSheet.webidl
new file mode 100644
index 00000000000..99ab3234705
--- /dev/null
+++ b/components/script/dom/webidls/CSSStyleSheet.webidl
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom/#the-cssstylesheet-interface
+[Exposed=Window]
+interface CSSStyleSheet : StyleSheet {
+  // readonly attribute CSSRule? ownerRule;
+  [SameObject] readonly attribute CSSRuleList cssRules;
+  // unsigned long insertRule(DOMString rule, unsigned long index);
+  // void deleteRule(unsigned long index);
+};
diff --git a/components/script/dom/webidls/CSSViewportRule.webidl b/components/script/dom/webidls/CSSViewportRule.webidl
new file mode 100644
index 00000000000..b1b73eb9c50
--- /dev/null
+++ b/components/script/dom/webidls/CSSViewportRule.webidl
@@ -0,0 +1,9 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/css-device-adapt/#css-viewport-rule-interface
+[Exposed=Window]
+interface CSSViewportRule : CSSRule {
+    // readonly attribute CSSStyleDeclaration style;
+};
diff --git a/components/script/dom/webidls/StyleSheet.webidl b/components/script/dom/webidls/StyleSheet.webidl
index b4f8bf94fae..a63e2a41f01 100644
--- a/components/script/dom/webidls/StyleSheet.webidl
+++ b/components/script/dom/webidls/StyleSheet.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://drafts.csswg.org/cssom/#the-stylesheet-interface
-[Exposed=(Window,Worker)]
+[Exposed=Window]
 interface StyleSheet {
   readonly attribute DOMString type_;
   readonly attribute DOMString? href;
diff --git a/components/script/dom/webidls/StyleSheetList.webidl b/components/script/dom/webidls/StyleSheetList.webidl
index 26ad1f72c3d..20360eb4ba4 100644
--- a/components/script/dom/webidls/StyleSheetList.webidl
+++ b/components/script/dom/webidls/StyleSheetList.webidl
@@ -4,7 +4,7 @@
 
 // https://drafts.csswg.org/cssom/#the-stylesheetlist-interface
 // [ArrayClass]
-[Exposed=(Window,Worker)]
+[Exposed=Window]
 interface StyleSheetList {
   getter StyleSheet? item(unsigned long index);
   readonly attribute unsigned long length;
diff --git a/components/style/selector_matching.rs b/components/style/selector_matching.rs
index 1f955c0a0de..c574c097a5a 100644
--- a/components/style/selector_matching.rs
+++ b/components/style/selector_matching.rs
@@ -388,7 +388,7 @@ impl Stylist {
             false
         }
         self.is_device_dirty |= stylesheets.iter().any(|stylesheet| {
-            mq_eval_changed(&stylesheet.rules, &self.device, &device)
+            mq_eval_changed(&stylesheet.rules.0.read(), &self.device, &device)
         });
 
         self.device = device;
diff --git a/components/style/stylesheets.rs b/components/style/stylesheets.rs
index 2d82653f06d..1538e9e0f25 100644
--- a/components/style/stylesheets.rs
+++ b/components/style/stylesheets.rs
@@ -7,6 +7,7 @@
 use {Atom, Prefix, Namespace};
 use cssparser::{AtRuleParser, Parser, QualifiedRuleParser, decode_stylesheet_bytes};
 use cssparser::{AtRuleType, RuleListParser, Token};
+use cssparser::ToCss as ParserToCss;
 use encoding::EncodingRef;
 use error_reporting::ParseErrorReporter;
 use font_face::{FontFaceRule, parse_font_face_block};
@@ -18,7 +19,9 @@ use properties::{PropertyDeclarationBlock, parse_property_declaration_list};
 use selector_impl::TheSelectorImpl;
 use selectors::parser::{Selector, parse_selector_list};
 use std::cell::Cell;
+use std::fmt;
 use std::sync::Arc;
+use style_traits::ToCss;
 use url::Url;
 use viewport::ViewportRule;
 
@@ -39,12 +42,20 @@ pub enum Origin {
     User,
 }
 
+#[derive(Debug, Clone)]
+pub struct CssRules(pub Arc<RwLock<Vec<CssRule>>>);
+
+impl From<Vec<CssRule>> for CssRules {
+    fn from(other: Vec<CssRule>) -> Self {
+        CssRules(Arc::new(RwLock::new(other)))
+    }
+}
 
 #[derive(Debug)]
 pub struct Stylesheet {
     /// List of rules in the order they were found (important for
     /// cascading order)
-    pub rules: Vec<CssRule>,
+    pub rules: CssRules,
     /// List of media associated with the Stylesheet.
     pub media: MediaList,
     pub origin: Origin,
@@ -59,7 +70,7 @@ pub struct UserAgentStylesheets {
 }
 
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum CssRule {
     // No Charset here, CSSCharsetRule has been removed from CSSOM
     // https://drafts.csswg.org/cssom/#changes-from-5-december-2013
@@ -89,7 +100,8 @@ impl CssRule {
             CssRule::Media(ref lock) => {
                 let media_rule = lock.read();
                 let mq = media_rule.media_queries.read();
-                f(&media_rule.rules, Some(&mq))
+                let rules = media_rule.rules.0.read();
+                f(&rules, Some(&mq))
             }
         }
     }
@@ -112,7 +124,7 @@ pub struct KeyframesRule {
 #[derive(Debug)]
 pub struct MediaRule {
     pub media_queries: Arc<RwLock<MediaList>>,
-    pub rules: Vec<CssRule>,
+    pub rules: CssRules,
 }
 
 #[derive(Debug)]
@@ -121,6 +133,41 @@ pub struct StyleRule {
     pub block: Arc<RwLock<PropertyDeclarationBlock>>,
 }
 
+impl StyleRule {
+    /// Serialize the group of selectors for this rule.
+    ///
+    /// https://drafts.csswg.org/cssom/#serialize-a-group-of-selectors
+    pub fn selectors_to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        let mut iter = self.selectors.iter();
+        try!(iter.next().unwrap().to_css(dest));
+        for selector in iter {
+            try!(write!(dest, ", "));
+            try!(selector.to_css(dest));
+        }
+        Ok(())
+    }
+}
+
+impl ToCss for StyleRule {
+    // https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSStyleRule
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        // Step 1
+        try!(self.selectors_to_css(dest));
+        // Step 2
+        try!(dest.write_str(" { "));
+        // Step 3
+        let declaration_block = self.block.read();
+        try!(declaration_block.to_css(dest));
+        // Step 4
+        if declaration_block.declarations.len() > 0 {
+            try!(write!(dest, " "));
+        }
+        // Step 5
+        try!(dest.write_str("}"));
+        Ok(())
+    }
+}
+
 
 impl Stylesheet {
     pub fn from_bytes_iter<I: Iterator<Item=Vec<u8>>>(
@@ -180,7 +227,7 @@ impl Stylesheet {
 
         Stylesheet {
             origin: origin,
-            rules: rules,
+            rules: rules.into(),
             media: Default::default(),
             dirty_on_viewport_size_change:
                 input.seen_viewport_percentages(),
@@ -208,7 +255,7 @@ impl Stylesheet {
     /// examined.
     #[inline]
     pub fn effective_rules<F>(&self, device: &Device, mut f: F) where F: FnMut(&CssRule) {
-        effective_rules(&self.rules, device, &mut f);
+        effective_rules(&self.rules.0.read(), device, &mut f);
     }
 }
 
@@ -251,7 +298,7 @@ rule_filter! {
     effective_keyframes_rules(Keyframes => KeyframesRule),
 }
 
-fn parse_nested_rules(context: &ParserContext, input: &mut Parser) -> Vec<CssRule> {
+fn parse_nested_rules(context: &ParserContext, input: &mut Parser) -> CssRules {
     let mut iter = RuleListParser::new_for_nested_rule(input,
                                                        NestedRuleParser { context: context });
     let mut rules = Vec::new();
@@ -265,7 +312,7 @@ fn parse_nested_rules(context: &ParserContext, input: &mut Parser) -> Vec<CssRul
             }
         }
     }
-    rules
+    rules.into()
 }
 
 
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index be42d076fc3..8a1745c16ca 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -255,7 +255,7 @@ pub extern "C" fn Servo_StyleSet_RemoveStyleSheet(raw_data: RawServoStyleSetBorr
 
 #[no_mangle]
 pub extern "C" fn Servo_StyleSheet_HasRules(raw_sheet: RawServoStyleSheetBorrowed) -> bool {
-    !Stylesheet::as_arc(&raw_sheet).rules.is_empty()
+    !Stylesheet::as_arc(&raw_sheet).rules.0.read().is_empty()
 }
 
 #[no_mangle]
diff --git a/python/tidy/servo_tidy/tidy.py b/python/tidy/servo_tidy/tidy.py
index bfb40bccd91..005a1bed24a 100644
--- a/python/tidy/servo_tidy/tidy.py
+++ b/python/tidy/servo_tidy/tidy.py
@@ -63,7 +63,7 @@ WEBIDL_STANDARDS = [
     "//dvcs.w3.org/hg",
     "//dom.spec.whatwg.org",
     "//domparsing.spec.whatwg.org",
-    "//drafts.csswg.org/cssom",
+    "//drafts.csswg.org",
     "//drafts.fxtf.org",
     "//encoding.spec.whatwg.org",
     "//fetch.spec.whatwg.org",
diff --git a/tests/unit/style/media_queries.rs b/tests/unit/style/media_queries.rs
index 04d0903a1b9..59628128082 100644
--- a/tests/unit/style/media_queries.rs
+++ b/tests/unit/style/media_queries.rs
@@ -29,7 +29,7 @@ fn test_media_rule<F>(css: &str, callback: F) where F: Fn(&MediaList, &str) {
     let stylesheet = Stylesheet::from_str(css, url, Origin::Author, Box::new(CSSErrorReporterTest),
                                           ParserContextExtraData::default());
     let mut rule_count = 0;
-    media_queries(&stylesheet.rules, &mut |mq| {
+    media_queries(&stylesheet.rules.0.read(), &mut |mq| {
         rule_count += 1;
         callback(mq, css);
     });
diff --git a/tests/unit/style/stylesheets.rs b/tests/unit/style/stylesheets.rs
index 7791fb14b9b..2efd471b99f 100644
--- a/tests/unit/style/stylesheets.rs
+++ b/tests/unit/style/stylesheets.rs
@@ -256,7 +256,7 @@ fn test_parse_stylesheet() {
                 ]
             })))
 
-        ],
+        ].into(),
     };
 
     assert_eq!(format!("{:#?}", stylesheet), format!("{:#?}", expected));
diff --git a/tests/wpt/harness/test/metadata/testharness/firefox/subdir/test_pref_reset.html.ini b/tests/wpt/harness/test/metadata/testharness/firefox/subdir/test_pref_reset.html.ini
index 6c9198d9bbf..de0043c5149 100644
--- a/tests/wpt/harness/test/metadata/testharness/firefox/subdir/test_pref_reset.html.ini
+++ b/tests/wpt/harness/test/metadata/testharness/firefox/subdir/test_pref_reset.html.ini
@@ -1,2 +1,3 @@
 [test_pref_reset.html]
+  type: testharness
   prefs: [@Reset]
diff --git a/tests/wpt/harness/test/metadata/testharness/firefox/test_pref_set.html.ini b/tests/wpt/harness/test/metadata/testharness/firefox/test_pref_set.html.ini
index bc9bfb9c413..ca005cd7558 100644
--- a/tests/wpt/harness/test/metadata/testharness/firefox/test_pref_set.html.ini
+++ b/tests/wpt/harness/test/metadata/testharness/firefox/test_pref_set.html.ini
@@ -1,3 +1,4 @@
 [test_pref_set.html]
+  type: testharness
   prefs: ["browser.display.foreground_color:#00FF00",
           "browser.display.background_color:#000000"]
diff --git a/tests/wpt/harness/test/metadata/testharness/subdir/testharness_1.html.ini b/tests/wpt/harness/test/metadata/testharness/subdir/testharness_1.html.ini
index db9393987b6..8be3d47e852 100644
--- a/tests/wpt/harness/test/metadata/testharness/subdir/testharness_1.html.ini
+++ b/tests/wpt/harness/test/metadata/testharness/subdir/testharness_1.html.ini
@@ -1,2 +1,3 @@
 [testharness_1.html]
+  type: testharness
   disabled: @False
\ No newline at end of file
diff --git a/tests/wpt/harness/test/metadata/testharness/tags/testharness_0.html.ini b/tests/wpt/harness/test/metadata/testharness/tags/testharness_0.html.ini
index fe8ffa48dd0..7fa297c7cea 100644
--- a/tests/wpt/harness/test/metadata/testharness/tags/testharness_0.html.ini
+++ b/tests/wpt/harness/test/metadata/testharness/tags/testharness_0.html.ini
@@ -1,4 +1,5 @@
 tags: [file-tag]
 
 [testharness_0.html]
+  type: testharness
   tags: [test-tag]
diff --git a/tests/wpt/harness/test/metadata/testharness/tags/testharness_1.html.ini b/tests/wpt/harness/test/metadata/testharness/tags/testharness_1.html.ini
index d6006a1551c..ecc07664f42 100644
--- a/tests/wpt/harness/test/metadata/testharness/tags/testharness_1.html.ini
+++ b/tests/wpt/harness/test/metadata/testharness/tags/testharness_1.html.ini
@@ -1,2 +1,3 @@
 [testharness_0.html]
+  type: testharness
   tags: [test-1-tag]
diff --git a/tests/wpt/harness/test/metadata/testharness/tags/testharness_2.html.ini b/tests/wpt/harness/test/metadata/testharness/tags/testharness_2.html.ini
index 25fbf55362d..d95e28832cc 100644
--- a/tests/wpt/harness/test/metadata/testharness/tags/testharness_2.html.ini
+++ b/tests/wpt/harness/test/metadata/testharness/tags/testharness_2.html.ini
@@ -1,4 +1,5 @@
 tags: [file-tag]
 
 [testharness_2.html]
+  type: testharness
   tags: [test-2-tag, @Reset]
diff --git a/tests/wpt/metadata-css/css-transitions-1_dev/html/changing-while-transition.htm.ini b/tests/wpt/metadata-css/css-transitions-1_dev/html/changing-while-transition.htm.ini
index e1464721388..4e9f379b7f9 100644
--- a/tests/wpt/metadata-css/css-transitions-1_dev/html/changing-while-transition.htm.ini
+++ b/tests/wpt/metadata-css/css-transitions-1_dev/html/changing-while-transition.htm.ini
@@ -2,6 +2,7 @@
   type: testharness
   [changing transition-property / values]
     expected: FAIL
+
   [changing transition-duration / values]
     expected: FAIL
 
diff --git a/tests/wpt/metadata-css/css21_dev/html4/color-applies-to-014.htm.ini b/tests/wpt/metadata-css/css21_dev/html4/color-applies-to-014.htm.ini
index a3379e753de..d3bb209de34 100644
--- a/tests/wpt/metadata-css/css21_dev/html4/color-applies-to-014.htm.ini
+++ b/tests/wpt/metadata-css/css21_dev/html4/color-applies-to-014.htm.ini
@@ -1,2 +1,3 @@
 [color-applies-to-014.htm]
-  disabled: https://github.com/servo/servo/pull/13870#issuecomment-255507790
+  type: reftest
+  disabled: https://github.com/servo/servo/pull/13870
diff --git a/tests/wpt/metadata-css/cssom-1_dev/html/index-003.htm.ini b/tests/wpt/metadata-css/cssom-1_dev/html/index-003.htm.ini
index b23072d78f6..e6f60a1c5f5 100644
--- a/tests/wpt/metadata-css/cssom-1_dev/html/index-003.htm.ini
+++ b/tests/wpt/metadata-css/cssom-1_dev/html/index-003.htm.ini
@@ -1,3 +1,8 @@
 [index-003.htm]
   type: testharness
-  expected: ERROR
+  [@import rule is expected to be @import url("main.css")]
+    expected: FAIL
+
+  [page rule is expected to be @page :first]
+    expected: FAIL
+
diff --git a/tests/wpt/metadata-css/cssom-1_dev/html/interfaces.htm.ini b/tests/wpt/metadata-css/cssom-1_dev/html/interfaces.htm.ini
index 78d6184cd70..02c46f56ee4 100644
--- a/tests/wpt/metadata-css/cssom-1_dev/html/interfaces.htm.ini
+++ b/tests/wpt/metadata-css/cssom-1_dev/html/interfaces.htm.ini
@@ -117,24 +117,9 @@
   [StyleSheet interface: attribute disabled]
     expected: FAIL
 
-  [CSSStyleSheet interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSStyleSheet interface object length]
-    expected: FAIL
-
-  [CSSStyleSheet interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [CSSStyleSheet interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
   [CSSStyleSheet interface: attribute ownerRule]
     expected: FAIL
 
-  [CSSStyleSheet interface: attribute cssRules]
-    expected: FAIL
-
   [CSSStyleSheet interface: operation insertRule(DOMString,unsigned long)]
     expected: FAIL
 
@@ -189,24 +174,9 @@
   [StyleSheetList interface: existence and properties of interface prototype object]
     expected: FAIL
 
-  [CSSRuleList interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSRuleList interface object length]
-    expected: FAIL
-
   [CSSRuleList interface: existence and properties of interface prototype object]
     expected: FAIL
 
-  [CSSRuleList interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
-  [CSSRuleList interface: operation item(unsigned long)]
-    expected: FAIL
-
-  [CSSRuleList interface: attribute length]
-    expected: FAIL
-
   [CSSRuleList must be primary interface of style_element.sheet.cssRules]
     expected: FAIL
 
@@ -222,90 +192,9 @@
   [CSSRuleList interface: style_element.sheet.cssRules must inherit property "length" with the proper type (1)]
     expected: FAIL
 
-  [CSSRule interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSRule interface object length]
-    expected: FAIL
-
-  [CSSRule interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
-  [CSSRule interface: constant STYLE_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant STYLE_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant CHARSET_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant CHARSET_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant IMPORT_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant IMPORT_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant MEDIA_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant MEDIA_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant FONT_FACE_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant FONT_FACE_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant PAGE_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant PAGE_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant MARGIN_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant MARGIN_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: constant NAMESPACE_RULE on interface object]
-    expected: FAIL
-
-  [CSSRule interface: constant NAMESPACE_RULE on interface prototype object]
-    expected: FAIL
-
-  [CSSRule interface: attribute type]
-    expected: FAIL
-
-  [CSSRule interface: attribute cssText]
-    expected: FAIL
-
   [CSSRule interface: attribute parentRule]
     expected: FAIL
 
-  [CSSRule interface: attribute parentStyleSheet]
-    expected: FAIL
-
-  [CSSStyleRule interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSStyleRule interface object length]
-    expected: FAIL
-
-  [CSSStyleRule interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [CSSStyleRule interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
   [CSSStyleRule interface: attribute selectorText]
     expected: FAIL
 
@@ -381,18 +270,6 @@
   [CSSImportRule interface: attribute styleSheet]
     expected: FAIL
 
-  [CSSGroupingRule interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSGroupingRule interface object length]
-    expected: FAIL
-
-  [CSSGroupingRule interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [CSSGroupingRule interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
   [CSSGroupingRule interface: attribute cssRules]
     expected: FAIL
 
@@ -402,18 +279,6 @@
   [CSSGroupingRule interface: operation deleteRule(unsigned long)]
     expected: FAIL
 
-  [CSSMediaRule interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSMediaRule interface object length]
-    expected: FAIL
-
-  [CSSMediaRule interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [CSSMediaRule interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
   [CSSMediaRule interface: attribute media]
     expected: FAIL
 
@@ -453,18 +318,6 @@
   [CSSMarginRule interface: attribute style]
     expected: FAIL
 
-  [CSSNamespaceRule interface: existence and properties of interface object]
-    expected: FAIL
-
-  [CSSNamespaceRule interface object length]
-    expected: FAIL
-
-  [CSSNamespaceRule interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [CSSNamespaceRule interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
   [CSSNamespaceRule interface: attribute namespaceURI]
     expected: FAIL
 
diff --git a/tests/wpt/metadata-css/geometry-1_dev/html/DOMMatrix-003.htm.ini b/tests/wpt/metadata-css/geometry-1_dev/html/DOMMatrix-003.htm.ini
index f48899ab692..29e6f751307 100644
--- a/tests/wpt/metadata-css/geometry-1_dev/html/DOMMatrix-003.htm.ini
+++ b/tests/wpt/metadata-css/geometry-1_dev/html/DOMMatrix-003.htm.ini
@@ -17,3 +17,4 @@
 
   [test skewY()]
     expected: FAIL
+
diff --git a/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-001.xht.ini b/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-001.xht.ini
index 52c1a3c5a0a..f1551700aef 100644
--- a/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-001.xht.ini
+++ b/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-001.xht.ini
@@ -1,6 +1,5 @@
 [DOMMatrix-001.xht]
   type: testharness
-
   [testConstructor1]
     expected: FAIL
 
diff --git a/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-003.xht.ini b/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-003.xht.ini
index b32671d9bc0..6dff066e704 100644
--- a/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-003.xht.ini
+++ b/tests/wpt/metadata-css/geometry-1_dev/xhtml1/DOMMatrix-003.xht.ini
@@ -17,3 +17,4 @@
 
   [test skewY()]
     expected: FAIL
+
diff --git a/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-001.xht.ini b/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-001.xht.ini
index 52c1a3c5a0a..f1551700aef 100644
--- a/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-001.xht.ini
+++ b/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-001.xht.ini
@@ -1,6 +1,5 @@
 [DOMMatrix-001.xht]
   type: testharness
-
   [testConstructor1]
     expected: FAIL
 
diff --git a/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-003.xht.ini b/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-003.xht.ini
index b32671d9bc0..6dff066e704 100644
--- a/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-003.xht.ini
+++ b/tests/wpt/metadata-css/geometry-1_dev/xhtml1print/DOMMatrix-003.xht.ini
@@ -17,3 +17,4 @@
 
   [test skewY()]
     expected: FAIL
+
diff --git a/tests/wpt/mozilla/meta/css/animations/basic-transition.html.ini b/tests/wpt/mozilla/meta/css/animations/basic-transition.html.ini
index 8d564f4e839..269b3cd3710 100644
--- a/tests/wpt/mozilla/meta/css/animations/basic-transition.html.ini
+++ b/tests/wpt/mozilla/meta/css/animations/basic-transition.html.ini
@@ -1,2 +1,3 @@
 [basic-transition.html]
+  type: reftest
   disabled: https://github.com/servo/servo/issues/13865
diff --git a/tests/wpt/mozilla/meta/css/inline_block_opacity_change.html.ini b/tests/wpt/mozilla/meta/css/inline_block_opacity_change.html.ini
new file mode 100644
index 00000000000..e77c99740ec
--- /dev/null
+++ b/tests/wpt/mozilla/meta/css/inline_block_opacity_change.html.ini
@@ -0,0 +1,4 @@
+[inline_block_opacity_change.html]
+  type: reftest
+  expected: PASS
+  disabled: https://github.com/servo/servo/issues/13360
diff --git a/tests/wpt/mozilla/tests/mozilla/interfaces.html b/tests/wpt/mozilla/tests/mozilla/interfaces.html
index 51c0b2cae63..debc89bf675 100644
--- a/tests/wpt/mozilla/tests/mozilla/interfaces.html
+++ b/tests/wpt/mozilla/tests/mozilla/interfaces.html
@@ -20,7 +20,17 @@ test_interfaces([
   "CharacterData",
   "CloseEvent",
   "CSS",
+  "CSSFontFaceRule",
+  "CSSGroupingRule",
+  "CSSKeyframesRule",
+  "CSSMediaRule",
+  "CSSNamespaceRule",
+  "CSSRule",
+  "CSSRuleList",
   "CSSStyleDeclaration",
+  "CSSStyleRule",
+  "CSSStyleSheet",
+  "CSSViewportRule",
   "DOMMatrix",
   "DOMMatrixReadOnly",
   "DOMPoint",
diff --git a/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js b/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js
index bc46462be50..15c6e2d60c6 100644
--- a/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js
+++ b/tests/wpt/mozilla/tests/mozilla/interfaces.worker.js
@@ -10,7 +10,6 @@ test_interfaces([
   "BeforeUnloadEvent",
   "Blob",
   "CloseEvent",
-  "CSS",
   "CSSStyleDeclaration",
   "DOMPoint",
   "DOMPointReadOnly",
@@ -50,8 +49,6 @@ test_interfaces([
   "Screen",
   "Storage",
   "StorageEvent",
-  "StyleSheet",
-  "StyleSheetList",
   "TextDecoder",
   "TextEncoder",
   "URL",