diff --git a/src/components/script/dom/document.rs b/src/components/script/dom/document.rs
index 9854bb7e386..b699f63f50f 100644
--- a/src/components/script/dom/document.rs
+++ b/src/components/script/dom/document.rs
@@ -478,20 +478,31 @@ impl Document {
         self.window.get().wait_until_safe_to_modify_dom();
     }
 
-    pub fn register_nodes_with_id(&mut self, root: &JS<Element>) {
-        foreach_ided_elements(root, |id: &DOMString, abstract_node: &JS<Element>| {
-            // TODO: "in tree order, within the context object's tree"
-            // http://dom.spec.whatwg.org/#dom-document-getelementbyid.
-            self.idmap.find_or_insert(id.clone(), abstract_node.clone());
-        });
+
+    /// Remove any existing association between the provided id and any elements in this document.
+    pub fn unregister_named_element(&mut self,
+                                    id: DOMString) {
+        self.idmap.remove(&id);
     }
 
-    pub fn unregister_nodes_with_id(&mut self, root: &JS<Element>) {
-        foreach_ided_elements(root, |id: &DOMString, _| {
-            // TODO: "in tree order, within the context object's tree"
-            // http://dom.spec.whatwg.org/#dom-document-getelementbyid.
-            self.idmap.pop(id);
+    /// Associate an element present in this document with the provided id.
+    pub fn register_named_element(&mut self,
+                                  element: &JS<Element>,
+                                  id: DOMString) {
+        assert!({
+            let node: JS<Node> = NodeCast::from(element);
+            node.is_in_doc()
         });
+
+        // TODO: support the case if multiple elements
+        // which haves same id are in the same document.
+        self.idmap.mangle(id, element,
+                          |_, new_element: &JS<Element>| -> JS<Element> {
+                              new_element.clone()
+                          },
+                          |_, old_element: &mut JS<Element>, new_element: &JS<Element>| {
+                              *old_element = new_element.clone();
+                          });
     }
 
     pub fn update_idmap(&mut self,
@@ -525,21 +536,3 @@ impl Document {
         }
     }
 }
-
-#[inline(always)]
-fn foreach_ided_elements(root: &JS<Element>, callback: |&DOMString, &JS<Element>|) {
-    let root: JS<Node> = NodeCast::from(root);
-    for node in root.traverse_preorder() {
-        if !node.is_element() {
-            continue;
-        }
-
-        let element: JS<Element> = ElementCast::to(&node);
-        match element.get().get_attribute(Null, "id") {
-            Some(id) => {
-                callback(&id.get().Value(), &element);
-            }
-            None => ()
-        }
-    }
-}
diff --git a/src/components/script/dom/element.rs b/src/components/script/dom/element.rs
index d7bbaa065a6..eed0bc9b237 100644
--- a/src/components/script/dom/element.rs
+++ b/src/components/script/dom/element.rs
@@ -646,6 +646,33 @@ impl Element {
     }
 }
 
+pub trait IElement {
+    fn bind_to_tree_impl(&self);
+    fn unbind_from_tree_impl(&self);
+}
+
+impl IElement for JS<Element> {
+    fn bind_to_tree_impl(&self) {
+        match self.get().get_attribute(Null, "id") {
+            Some(attr) => {
+                let mut doc = self.get().node.owner_doc();
+                doc.get_mut().register_named_element(self, attr.get().Value());
+            }
+            _ => ()
+        }
+    }
+
+    fn unbind_from_tree_impl(&self) {
+        match self.get().get_attribute(Null, "id") {
+            Some(attr) => {
+                let mut doc = self.get().node.owner_doc();
+                doc.get_mut().unregister_named_element(attr.get().Value());
+            }
+            _ => ()
+        }
+    }
+}
+
 fn get_attribute_parts(name: DOMString) -> (Option<~str>, ~str) {
     //FIXME: Throw for XML-invalid names
     //FIXME: Throw for XMLNS-invalid names
diff --git a/src/components/script/dom/node.rs b/src/components/script/dom/node.rs
index a0357c92ab4..419b02c844a 100644
--- a/src/components/script/dom/node.rs
+++ b/src/components/script/dom/node.rs
@@ -14,7 +14,7 @@ use dom::bindings::utils;
 use dom::characterdata::CharacterData;
 use dom::document::Document;
 use dom::documenttype::DocumentType;
-use dom::element::{Element, ElementTypeId, HTMLAnchorElementTypeId};
+use dom::element::{Element, ElementTypeId, HTMLAnchorElementTypeId, IElement};
 use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::nodelist::{NodeList};
 use dom::text::Text;
@@ -396,11 +396,13 @@ impl NodeHelpers for JS<Node> {
     // http://dom.spec.whatwg.org/#node-is-inserted
     fn node_inserted(&self) {
         assert!(self.parent_node().is_some());
-        let mut document = self.get().owner_doc();
+        let document = self.get().owner_doc();
 
-        // Register elements having "id" attribute to the owner doc.
-        if self.is_element() {
-            document.get_mut().register_nodes_with_id(&ElementCast::to(self));
+        for node in self.traverse_preorder() {
+            if node.is_element() {
+                let element: JS<Element> = ElementCast::to(&node);
+                element.bind_to_tree_impl();
+            }
         }
 
         document.get().content_changed();
@@ -409,11 +411,13 @@ impl NodeHelpers for JS<Node> {
     // http://dom.spec.whatwg.org/#node-is-removed
     fn node_removed(&self) {
         assert!(self.parent_node().is_none());
-        let mut document = self.get().owner_doc();
+        let document = self.get().owner_doc();
 
-        // Unregister elements having "id".
-        if self.is_element() {
-            document.get_mut().unregister_nodes_with_id(&ElementCast::to(self));
+        for node in self.traverse_preorder() {
+            if node.is_element() {
+                let element: JS<Element> = ElementCast::to(&node);
+                element.unbind_from_tree_impl();
+            }
         }
 
         document.get().content_changed();