jQuery.fn.dropdown_menu = function() {
  return this.each(function() {
      $(this).find("li").hover(
        function(){ /* mouse over effect */
            $(this).find('ul:first:hidden').css({visibility: "visible"}).show(400);
		},function(){ /* mouse out effect */
		    $(this).find('ul:first').css({visibility: "hidden"});
		});
  });
};
$(document).ready(function(event){
  $("#mainmenu").dropdown_menu();
});