Address http://lists.w3.org/Archives/Public/www-style/2009Oct/0194.html

Author: fantasai

selectors3/Overview.html

@@ -1877,10 +1877,11 @@ <h4><a name=negation></a>6.6.7. The negation pseudo-class</h4>
 <p>The negation pseudo-class, <code>:not(<var>X</var>)</code>, is a
 functional notation taking a <a href="#simple-selectors-dfn">simple
 selector</a> (excluding the negation pseudo-class itself) as an argument.
-It represents an element that is not represented by the argument.
+It represents an element that is not represented by its argument.
 
-<p class="note"><strong>Note:</strong> Since pseudo-elements are not
-simple selectors, they are not a valid argument to <code>:not()</code>.</p>
+<p>Negations may not be nested; <code>:not(:not(...))</code> is invalid.
+Note also that since pseudo-elements are not simple selectors, they are
+not a valid argument to <code>:not()</code>.</p>
 
 <div class="example">
   <p>Examples:</p>