function dlhover(){
  if (!document.getElementById) return

  var dl = document.getElementsByTagName('dl');
  for(var i = 0; i < dl.length; i++){
   dl[i].onmouseover = function(){
    this.className = 'hover';
   }
   dl[i].onmouseout  = function(){
    this.className = '';
   }
  }
}
window.onload = dlhover;