onload = function(){
  if(document.getElementById){
   var navRoot = document.getElementsByTagName('TR');
    for(var i=0; i<navRoot.length; i++){
      for(var j=0; j<navRoot[i].childNodes.length; j++){
          node = navRoot[i].childNodes[j];
        if(node.nodeName == 'TD'){
           node.onmouseover = function(){
           this.className += 'over';
          }
           node.onmouseout = function(){
           this.className = this.className.replace('over', '');
          }
        }
      }
    }
  }
}