diff --git a/components/style/attr.rs b/components/style/attr.rs
index 1d0d555d509..92ab7700fb8 100644
--- a/components/style/attr.rs
+++ b/components/style/attr.rs
@@ -539,28 +539,18 @@ pub fn parse_length(mut value: &str) -> LengthOrPercentageOrAuto {
     value = value.trim_start_matches(HTML_SPACE_CHARACTERS);
 
     // Step 4
-    if value.is_empty() {
-        return LengthOrPercentageOrAuto::Auto;
-    }
-
-    // Step 5
-    if value.starts_with('+') {
-        value = &value[1..]
-    }
-
-    // Steps 6 & 7
     match value.chars().nth(0) {
         Some('0'..='9') => {},
         _ => return LengthOrPercentageOrAuto::Auto,
     }
 
-    // Steps 8 to 13
+    // Steps 5 to 8
     // We trim the string length to the minimum of:
     // 1. the end of the string
     // 2. the first occurence of a '%' (U+0025 PERCENT SIGN)
     // 3. the second occurrence of a '.' (U+002E FULL STOP)
     // 4. the occurrence of a character that is neither a digit nor '%' nor '.'
-    // Note: Step 10 is directly subsumed by FromStr::from_str
+    // Note: Step 7.4 is directly subsumed by FromStr::from_str
     let mut end_index = value.len();
     let (mut found_full_stop, mut found_percent) = (false, false);
     for (i, ch) in value.chars().enumerate() {
diff --git a/tests/unit/style/attr.rs b/tests/unit/style/attr.rs
index 261d6d8f98b..9bcfa2be522 100644
--- a/tests/unit/style/attr.rs
+++ b/tests/unit/style/attr.rs
@@ -66,7 +66,8 @@ pub fn test_parse_length() {
 
     check("0", LengthOrPercentageOrAuto::Length(Au::from_px(0)));
     check("0.000%", LengthOrPercentageOrAuto::Percentage(0.0));
-    check("+5.82%", LengthOrPercentageOrAuto::Percentage(0.0582));
+    check("+5.82%", LengthOrPercentageOrAuto::Auto);
+    check("5.82%", LengthOrPercentageOrAuto::Percentage(0.0582));
     check(
         "5.82",
         LengthOrPercentageOrAuto::Length(Au::from_f64_px(5.82)),
diff --git a/tests/wpt/metadata/html/rendering/dimension-attributes.html.ini b/tests/wpt/metadata/html/rendering/dimension-attributes.html.ini
index b0a5e5d8414..6583da6a4c8 100644
--- a/tests/wpt/metadata/html/rendering/dimension-attributes.html.ini
+++ b/tests/wpt/metadata/html/rendering/dimension-attributes.html.ini
@@ -2552,21 +2552,12 @@
   [<td height="20.25E2"> mapping to height]
     expected: FAIL
 
-  [<hr width="   +200.25in    "> mapping to width]
-    expected: FAIL
-
   [<object vspace="20.25e2"> mapping to marginTop]
     expected: FAIL
 
   [<marquee hspace="20.25e2"> mapping to marginRight]
     expected: FAIL
 
-  [<td width="   +200.25%    "> mapping to width]
-    expected: FAIL
-
-  [<iframe width="+200"> mapping to width]
-    expected: FAIL
-
   [<object hspace="20.25e2"> mapping to marginRight]
     expected: FAIL
 
@@ -2579,30 +2570,12 @@
   [<input width="20.25e2"> mapping to width]
     expected: FAIL
 
-  [<td width="   +200.25in    "> mapping to width]
-    expected: FAIL
-
-  [<iframe height="   +200.25in    "> mapping to height]
-    expected: FAIL
-
   [<img hspace="20.25E2"> mapping to marginLeft]
     expected: FAIL
 
   [<marquee vspace="20.25E2"> mapping to marginTop]
     expected: FAIL
 
-  [<img width="+200%"> mapping to width]
-    expected: FAIL
-
-  [<img height="   +200in    "> mapping to height]
-    expected: FAIL
-
-  [<table width="   +200.25%    "> mapping to width]
-    expected: FAIL
-
-  [<iframe width="   +200.25%abc"> mapping to width]
-    expected: FAIL
-
   [<embed vspace="20.25E2"> mapping to marginTop]
     expected: FAIL
 
@@ -2618,24 +2591,12 @@
   [<embed hspace="20.25e2"> mapping to marginRight]
     expected: FAIL
 
-  [<td width="   +200.25%abc"> mapping to width]
-    expected: FAIL
-
   [<embed height="20.25e2"> mapping to height]
     expected: FAIL
 
-  [<td width="+200"> mapping to width]
-    expected: FAIL
-
-  [<hr width="+200"> mapping to width]
-    expected: FAIL
-
   [<marquee hspace="20.25e2"> mapping to marginLeft]
     expected: FAIL
 
-  [<img height="+0%"> mapping to height]
-    expected: FAIL
-
   [<input vspace="20.25E2"> mapping to marginTop]
     expected: FAIL
 
@@ -2648,12 +2609,6 @@
   [<input hspace="20.25e2"> mapping to marginLeft]
     expected: FAIL
 
-  [<iframe height="+200"> mapping to height]
-    expected: FAIL
-
-  [<iframe height="   +200in    "> mapping to height]
-    expected: FAIL
-
   [<table height="20.25E2"> mapping to height]
     expected: FAIL
 
@@ -2675,21 +2630,9 @@
   [<img vspace="20.25E2"> mapping to marginBottom]
     expected: FAIL
 
-  [<iframe width="   +200in    "> mapping to width]
-    expected: FAIL
-
-  [<iframe width="+200%"> mapping to width]
-    expected: FAIL
-
-  [<td width="   +200in    "> mapping to width]
-    expected: FAIL
-
   [<tr height="20.25E2"> mapping to height]
     expected: FAIL
 
-  [<img height="   +200.25%abc"> mapping to height]
-    expected: FAIL
-
   [<marquee width="20.25E2"> mapping to width]
     expected: FAIL
 
@@ -2699,120 +2642,51 @@
   [<input vspace="20.25E2"> mapping to marginBottom]
     expected: FAIL
 
-  [<table width="   +200in    "> mapping to width]
-    expected: FAIL
-
   [<marquee vspace="20.25e2"> mapping to marginBottom]
     expected: FAIL
 
   [<img vspace="20.25E2"> mapping to marginTop]
     expected: FAIL
 
-  [<table width="   +200.25in    "> mapping to width]
-    expected: FAIL
-
-  [<img width="   +200.25%    "> mapping to width]
-    expected: FAIL
-
   [<embed hspace="20.25e2"> mapping to marginLeft]
     expected: FAIL
 
-  [<hr width="   +200.25%abc"> mapping to width]
-    expected: FAIL
-
   [<embed hspace="20.25E2"> mapping to marginRight]
     expected: FAIL
 
-  [<hr width="+0%"> mapping to width]
-    expected: FAIL
-
-  [<img width="+0%"> mapping to width]
-    expected: FAIL
-
-  [<iframe height="   +200.25%abc"> mapping to height]
-    expected: FAIL
-
-  [<img width="+200"> mapping to width]
-    expected: FAIL
-
   [<input width="20.25E2"> mapping to width]
     expected: FAIL
 
   [<marquee height="20.25e2"> mapping to height]
     expected: FAIL
 
-  [<hr width="+0"> mapping to width]
-    expected: FAIL
-
   [<object hspace="20.25E2"> mapping to marginLeft]
     expected: FAIL
 
-  [<img width="+0"> mapping to width]
-    expected: FAIL
-
-  [<iframe width="+0"> mapping to width]
-    expected: FAIL
-
   [<img hspace="20.25e2"> mapping to marginRight]
     expected: FAIL
 
   [<input hspace="20.25e2"> mapping to marginRight]
     expected: FAIL
 
-  [<iframe height="+200%"> mapping to height]
-    expected: FAIL
-
-  [<hr width="   +200in    "> mapping to width]
-    expected: FAIL
-
-  [<img height="+200"> mapping to height]
-    expected: FAIL
-
-  [<img height="+0"> mapping to height]
-    expected: FAIL
-
   [<embed hspace="20.25E2"> mapping to marginLeft]
     expected: FAIL
 
-  [<img width="   +200.25in    "> mapping to width]
-    expected: FAIL
-
-  [<table width="+200%"> mapping to width]
-    expected: FAIL
-
   [<object vspace="20.25E2"> mapping to marginBottom]
     expected: FAIL
 
-  [<img height="   +200.25%    "> mapping to height]
-    expected: FAIL
-
-  [<table width="   +200.25%abc"> mapping to width]
-    expected: FAIL
-
   [<object height="20.25e2"> mapping to height]
     expected: FAIL
 
-  [<iframe width="   +200.25%    "> mapping to width]
-    expected: FAIL
-
-  [<table width="+200"> mapping to width]
-    expected: FAIL
-
   [<embed width="20.25e2"> mapping to width]
     expected: FAIL
 
   [<embed vspace="20.25E2"> mapping to marginBottom]
     expected: FAIL
 
-  [<iframe width="   +200.25in    "> mapping to width]
-    expected: FAIL
-
   [<embed vspace="20.25e2"> mapping to marginBottom]
     expected: FAIL
 
-  [<iframe height="+0%"> mapping to height]
-    expected: FAIL
-
   [<video width="20.25E2"> mapping to width]
     expected: FAIL
 
@@ -2822,57 +2696,33 @@
   [<video height="20.25e2"> mapping to height]
     expected: FAIL
 
-  [<hr width="+200%"> mapping to width]
-    expected: FAIL
-
   [<tr height="20.25e2"> mapping to height]
     expected: FAIL
 
-  [<img width="   +200.25%abc"> mapping to width]
-    expected: FAIL
-
   [<input hspace="20.25E2"> mapping to marginRight]
     expected: FAIL
 
-  [<iframe height="+0"> mapping to height]
-    expected: FAIL
-
   [<video width="20.25e2"> mapping to width]
     expected: FAIL
 
   [<marquee width="20.25e2"> mapping to width]
     expected: FAIL
 
-  [<hr width="   +200.25%    "> mapping to width]
-    expected: FAIL
-
   [<marquee hspace="20.25E2"> mapping to marginRight]
     expected: FAIL
 
   [<col width="20.25e2"> mapping to width]
     expected: FAIL
 
-  [<iframe height="   +200.25%    "> mapping to height]
-    expected: FAIL
-
   [<embed width="20.25E2"> mapping to width]
     expected: FAIL
 
-  [<iframe width="+0%"> mapping to width]
-    expected: FAIL
-
   [<input vspace="20.25e2"> mapping to marginBottom]
     expected: FAIL
 
   [<input hspace="20.25E2"> mapping to marginLeft]
     expected: FAIL
 
-  [<img height="+200%"> mapping to height]
-    expected: FAIL
-
-  [<td width="+200%"> mapping to width]
-    expected: FAIL
-
   [<marquee vspace="20.25e2"> mapping to marginTop]
     expected: FAIL
 
@@ -2882,9 +2732,6 @@
   [<object hspace="20.25e2"> mapping to marginLeft]
     expected: FAIL
 
-  [<img height="   +200.25in    "> mapping to height]
-    expected: FAIL
-
   [<input vspace="20.25e2"> mapping to marginTop]
     expected: FAIL
 
@@ -2900,9 +2747,6 @@
   [<marquee hspace="20.25E2"> mapping to marginLeft]
     expected: FAIL
 
-  [<img width="   +200in    "> mapping to width]
-    expected: FAIL
-
   [<object height="20.25E2"> mapping to height]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/html/rendering/non-replaced-elements/the-hr-element-0/width.html.ini b/tests/wpt/metadata/html/rendering/non-replaced-elements/the-hr-element-0/width.html.ini
deleted file mode 100644
index 3c08b64d3ea..00000000000
--- a/tests/wpt/metadata/html/rendering/non-replaced-elements/the-hr-element-0/width.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[width.html]
-  expected: FAIL