[cssom] Editorial fix and WebIDL validation fix

Author: Simon Pieters

cssom/Overview.html

@@ -2213,10 +2213,10 @@ <h4 id="the-cssstyledeclaration-interface"><span class="secno">6.5.1 </span>The
 <var>property</var>.</p>
 
 <pre class="idl">partial interface <a href="#cssstyledeclaration">CSSStyleDeclaration</a> {
-  [TreatNullAs=EmptyString] attribute DOMString <var title="dom-CSSStyleDeclaration-attribute"><a href="#dom-cssstyledeclaration-attribute">attribute</a></var>;
+  [TreatNullAs=EmptyString] attribute DOMString _<var title="dom-CSSStyleDeclaration-attribute"><a href="#dom-cssstyledeclaration-attribute">attribute</a></var>;
 };</pre>
 
-<p>The <dfn id="dom-cssstyledeclaration-attribute" title="dom-CSSStyleDeclaration-attribute"><code><var>attribute</var></code></dfn> attribute must return the result of invoking
+<p>The <dfn id="dom-cssstyledeclaration-attribute" title="dom-CSSStyleDeclaration-attribute"><code><var>attribute</var></code></dfn> attribute, on getting, must return the result of invoking
 <code title="dom-CSSStyleDeclaration-getPropertyValue"><a href="#dom-cssstyledeclaration-getpropertyvalue">getPropertyValue()</a></code> with as
 argument the result of running the <a href="#idl-attribute-to-css-property">IDL attribute to CSS property</a>
 algorithm for <var>attribute</var>.</p>

cssom/Overview.src.html

@@ -2143,10 +2143,10 @@ <h4>The <code title>CSSStyleDeclaration</code> Interface</h4>
 <var>property</var>.</p>
 
 <pre class=idl>partial interface <span>CSSStyleDeclaration</span> {
-  [TreatNullAs=EmptyString] attribute DOMString <var title=dom-CSSStyleDeclaration-attribute>attribute</var>;
+  [TreatNullAs=EmptyString] attribute DOMString _<var title=dom-CSSStyleDeclaration-attribute>attribute</var>;
 };</pre>
 
-<p>The <dfn title=dom-CSSStyleDeclaration-attribute><code><var>attribute</var></code></dfn> attribute must return the result of invoking
+<p>The <dfn title=dom-CSSStyleDeclaration-attribute><code><var>attribute</var></code></dfn> attribute, on getting, must return the result of invoking
 <code title=dom-CSSStyleDeclaration-getPropertyValue>getPropertyValue()</code> with as
 argument the result of running the <span>IDL attribute to CSS property</span>
 algorithm for <var>attribute</var>.</p>