function initializeNavBar(){

 topRoot = document.getElementById("navbar");
 for (i=0; i<topRoot.childNodes.length; i++) {
   nodeAt = topRoot.childNodes[i];
   if (nodeAt.nodeName=="LI") {
       nodeAt.onmouseover=function() {
         this.className =" dropdown";
       }
       nodeAt.onmouseout=function() {
         this.className="";
       }
   }
 }
}

window.onload=initializeNavBar;