use referer instead of static homepage URL

_layouts/base.html

@@ -14,7 +14,7 @@
         <div id="container">
             {{ content }}
             <div id="footer">
-                <p>Copyright &copy; 2011 Ben Kurtovic &bull; <a href="http://github.com/earwig/earwig.github.com">View Source</a> &bull; <a href="http://validator.w3.org/check?uri=http%3A%2F%2Fearwig.github.com%2F">Valid XHTML 1.0 Strict</a></p>
+                <p>Copyright &copy; 2011 Ben Kurtovic &bull; <a href="http://github.com/earwig/earwig.github.com">View Source</a> &bull; <a href="http://validator.w3.org/check?uri=referer">Valid XHTML 1.0 Strict</a></p>
             </div>
         </div>
     </body>