function initPage()
{
var nav = document.getElementById("top_menu");
if (nav)
{
 var nodes = nav.getElementsByTagName("li");
 for (var i = 0; i < nodes.length; i++)
 {  
   nodes[i].onmouseover = function () 
   {
    this.className += " hover";
   }
   nodes[i].onmouseout = function ()
   {
    this.className = this.className.replace(" hover", "");
   }
 }
}
}
if (window.attachEvent) window.attachEvent("onload", initPage);