menuHover = function() {
 var Els = document.getElementById("nav").getElementsByTagName("LI");
 for (var i=0; i<Els.length; i++) {
  Els[i].onmouseover=function() {
   this.className+=" over";
  }
  Els[i].onmouseout=function() {
   this.className=this.className.replace(new RegExp(" over\\b"), "");
  }
 }
}
if (window.attachEvent) window.attachEvent("onload", menuHover);