<div id="menu">
 <ul>
  <li><a href="">网站首页</a></li>
  <li><a href="">免费模板</a></li>
 </ul>
</div>
<script type="text/javascript" language="javascript">
var nav = document.getElementById("menu");
var links = nav.getElementsByTagName("li");
var lilen = nav.getElementsByTagName("a");
var currenturl = document.location.href;
var last = 0;
for (var i=0;i<links.length;i++)
{
   var linkurl =  lilen[i].getAttribute("href");
     if(currenturl.indexOf(linkurl)!=-1)
        {
         last = i;
        }
}
         links[last].className = "menu_on";
</script>