$(window).load(function(){
//cache nav  
         var nav = $("#topnav");  
   
         //add indicators and hovers to submenu parents  
         nav.find("li").each(function() {  
             if ($(this).find("ul").length > 0) {  
   
                 //show subnav on hover  
                 $(this).mouseenter(function() {  
                     $(this).find("ul").stop(true, true).slideDown();  
                 });  
   
                 //hide submenus on exit  
                 $(this).mouseleave(function() {  
                     $(this).find("ul").stop(true, true).slideUp();  
                 });  
             }  
         });  

});