window.addEvent('domready', function(){
                $('drop_down_menu').getElements('li.menu').each( function( elem ){
                        var list = elem.getElement('ul.links');
                        var myFx = new Fx.Slide(list).hide();
                        elem.addEvents({
                                'mouseenter' : function(){
                                        myFx.cancel();
                                        myFx.slideIn();
                                },
                                'mouseleave' : function(){
                                        myFx.cancel();
                                        myFx.slideOut();
                                }
                        });
                })
        });