Restore case-insensitive attribute value selector matching

Reverts 78f1994. Fixes
https://www.w3.org/Bugs/Public/show_bug.cgi?id=24005.

source

@@ -69656,8 +69656,67 @@ contradict people?
   comparison is <span>case-sensitive</span>.</p>
   <!-- http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=2624 -->
 
-  <p>Everything else must be treated as entirely <span>case-sensitive</span> for the purposes of
-  selector matching. This includes:</p>
+  <p>Attribute selectors on an <span title="HTML elements">HTML element</span> in an
+  <span title="HTML documents">HTML document</span> must treat the <em>values</em> of attributes
+  with the following names as <span>ASCII case-insensitive</span>, with one
+  exception as noted below:</p>
+
+  <!-- based on Mozilla's list, which was itself based on HTML4 -->
+  <!-- WebKit's was identical at the time of writing except as noted below -->
+  <ul class="brief">
+   <li><code title="">accept</code>
+   <li><code title="">accept-charset</code>
+   <li><code title="">align</code>
+   <li><code title="">alink</code>
+   <li><code title="">axis</code>
+   <li><code title="">bgcolor</code>
+   <li><code title="">charset</code>
+   <li><code title="">checked</code>
+   <li><code title="">clear</code>
+   <li><code title="">codetype</code>
+   <li><code title="">color</code>
+   <li><code title="">compact</code>
+   <li><code title="">declare</code>
+   <li><code title="">defer</code>
+   <li><code title="">dir</code>
+   <li><code title="">direction</code> <!-- not in WebKit -->
+   <li><code title="">disabled</code>
+   <li><code title="">enctype</code>
+   <li><code title="">face</code>
+   <li><code title="">frame</code>
+   <li><code title="">hreflang</code>
+   <li><code title="">http-equiv</code>
+   <li><code title="">lang</code>
+   <li><code title="">language</code>
+   <li><code title="">link</code>
+   <li><code title="">media</code>
+   <li><code title="">method</code>
+   <li><code title="">multiple</code>
+   <li><code title="">nohref</code>
+   <li><code title="">noresize</code>
+   <li><code title="">noshade</code>
+   <li><code title="">nowrap</code>
+   <li><code title="">readonly</code>
+   <li><code title="">rel</code>
+   <li><code title="">rev</code>
+   <li><code title="">rules</code>
+   <li><code title="">scope</code>
+   <li><code title="">scrolling</code>
+   <li><code title="">selected</code>
+   <li><code title="">shape</code>
+   <li><code title="">target</code>
+   <li><code title="">text</code>
+   <li><code title="">type</code> (except as specified below)
+   <li><code title="">valign</code>
+   <li><code title="">valuetype</code>
+   <li><code title="">vlink</code>
+  </ul>
+
+  <p>The exception to the list above is the <code title="attr-ol-type">type</code> attribute on
+  <code>ol</code> elements, which must be treated as <span>case-sensitive</span>.</p>
+
+  <p>All other attribute values and everything else must be treated as entirely
+  <span>case-sensitive</span> for the purposes of selector matching. This includes:</p>
 
   <ul class=brief>
    <li> IDs and classes in <span>no-quirks mode</span> and <span>limited-quirks mode</span>
@@ -69666,7 +69725,6 @@ contradict people?
    <li> the names of attributes of elements not in the <span>HTML namespace</span>
    <li> the names of attributes of <span>HTML elements</span> in <span>XML documents</span>
    <li> the names of attributes that themselves have namespaces
-   <li> all attribute values
   </ul>