$$(".submenu").each( function(e){ e.hide(); } )
$$("#menu li").invoke("observe", "mouseover", function() { if( this.down(".submenu") != undefined ){ this.down(".submenu").show(); } });
$$("#menu li").invoke("observe", "mouseout", function() { if( this.down(".submenu") != undefined ){ this.down(".submenu").hide(); } });