Menu - SlideDown SlideUp

Menu - SlideDown SlideUp

Hi all

Im pretty new to the JQuery world, and am trying to modify the following code so that it slidesDown and slidesUp on hover (mouseover/mouseout), however the mouseout isnt working properly as it dissapears completely rather than doing the slideUp effect



   function menu(){
   $(" #nav li").hover(function(){
         $(this).find('ul:first').css({visibility: "visible",display: "none"}).slideDown('fast').show();
         },function(){
         $(this).find('ul:first').css({visibility: "visible", display: "none"}).slideUp('slow');
         });
   }

   $(document).ready(function(){               
   menu();
   });


Thanks