More precise wording on URL resolution

Author: fantasai

css-style-attr/Overview.html

@@ -258,8 +258,10 @@ <h2 id=interpret><span class=secno>5. </span>Cascading and Interpretation</h2>
    styling attributes are cascaded together. <a href="#CSS21"
    rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> Relative URLs in the style
    data must be resolved relative to the styling attribute's element (or to
-   the document if per-element resolution is not defined) at the time of
-   parsing.
+   the document if per-element resolution is not defined) when the
+   attribute's value is parsed<!-- so dynamic changes to
+the base URL don't affect the CSS ~Hixie -->.
+   
 
   <p>Aside from the differences in cascading, the declarations in a styling
    attribute must be interpreted exactly as if they were given in a CSS style

css-style-attr/Overview.src.html

@@ -148,7 +148,8 @@ <h2 id="interpret">Cascading and Interpretation</h2>
 how style sheets and styling attributes are cascaded together. [[!CSS21]]
 Relative URLs in the style data must be resolved relative to the styling
 attribute's element (or to the document if per-element resolution is not
-defined) at the time of parsing.
+defined) when the attribute's value is parsed<!-- so dynamic changes to
+the base URL don't affect the CSS ~Hixie -->.
 
 <p>Aside from the differences in cascading, the declarations in a styling
 attribute must be interpreted exactly as if they were given in a CSS