$(document).ready(function(){ 

     $("#map_objects a").hover(
        function(){
            $(".map_desc").css("display","none");
            li = $(this).parent();
            $(".map_desc", li).fadeIn("fast");;
            $(".bubble", li).css("display","none");
        },
        function(){
            $(".map_desc", li).css("display","none");
            $(".bubble", li).css("display","block");
        }
     );
});