Use a local copy of the valid HTML 4.01 icon.

[SVN r53048]

binders.html

@@ -144,7 +144,7 @@ binder2nd(const Operation& x,
   <hr>
 
   <p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src=
-  "http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Transitional"
+  "../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional"
   height="31" width="88"></a></p>
 
   <p>Revised