(function($){
 $(function(){
  $('.menu_sub').bind({
   mouseenter: function() {
    $("img", this).attr('src', $("img", this).attr('src').replace('_off', '_on'));
    var $btn=$(this).children("ul");
    if(!$btn.is(':animated')) $btn.slideDown({duration: 300, easing: "easeOutQuart", complete: "callback"});
   },
   mouseleave: function() {
    $(this).children("ul").slideUp({duration: 500, easing: "easeOutQuart", complete: "callback"});
    $("img", this).attr('src', $("img", this).attr('src').replace('_on', '_off'));
   }
  });
  
 });
})(jQuery);