function menuItemOver(e) {
   if (this.className.search(/\bhover\b/g) == -1) { this.className += ' hover'; }
}

function menuItemOut(e) {
   this.className = this.className.replace(/\s*\bhover\b/g, '');
}

function enhanceMenu()
{
   if (document.all) { // IE only
      var menu = document.getElementById('main_menu');
      if (menu) {
         var lis = menu.getElementsByTagName('li');
         if (lis) {
            for (var i = 0; i < lis.length; i++) {
               var node = lis[i];
               // Add hover behavior
               node.onmouseover = menuItemOver;
               node.onmouseout  = menuItemOut;
               //
               node = null;
            }
            lis = null;
         }
         menu = null;
      }
   }
}

if (document.getElementById && document.getElementsByTagName) {
   window.onload = enhanceMenu;
}