Wording tweak.

Author: tabatkins

css3-images/Overview.html

@@ -610,8 +610,8 @@ <h4 id=image-fallbacks><span class=secno>3.2.2. </span> Image Fallbacks</h4>
   </div>
 
   <p>If a URL uses a fragment identifier syntax that the implementation does
-   not understand, or does not support for that type of image, the URL must
-   be treated as representing an <a href="#invalid-image"><i>invalid
+   not understand, or does not consider valid for that type of image, the URL
+   must be treated as representing an <a href="#invalid-image"><i>invalid
    image</i></a>. <span class=note>This error-handling is limited to image(),
    and not in the definition of URL, for legacy compat reasons.</span>
 

css3-images/Overview.src.html

@@ -270,7 +270,7 @@ <h4>
 		<p>Now, the black won't show at all if the image loads, but if for whatever reason the image fails, it'll pop in and prevent the white text from being set against a white background.</p>
 	</div>
 
-	<p>If a URL uses a fragment identifier syntax that the implementation does not understand, or does not support for that type of image, the URL must be treated as representing an <i>invalid image</i>. <span class='note'>This error-handling is limited to image(), and not in the definition of URL, for legacy compat reasons.</span></p>
+	<p>If a URL uses a fragment identifier syntax that the implementation does not understand, or does not consider valid for that type of image, the URL must be treated as representing an <i>invalid image</i>. <span class='note'>This error-handling is limited to image(), and not in the definition of URL, for legacy compat reasons.</span></p>
 
 	<div class='example'>
 		<p>For example, if a future specification defined a way to refer to a specific frame of an animated GIF with a fragment identifier, an author could write the following to get newer browsers to use the GIF's frame, and older browsers to instead download the fallback image:</p>