window.addEvent('domready', function(){
    $('drop_down_menu').getElements('li.menu').each( function( elem ){
      var list = elem.getElement('ul.links');  
      list.morph({opacity: 0.9});
      if (navigator.appName=='Opera') {
        list.style.marginTop="12px";
      }
      var myFx = new Fx.Slide(list).hide();  
      elem.addEvents({
        'mouseenter' : function(){           
          myFx.cancel();
          myFx.slideIn();          
        },
        'mouseleave' : function(){
          myFx.cancel();
          myFx.slideOut();        
        }
      });  
    })
  });