var name = "#menu";  
 var menuYloc = null;  
   
 $(document).ready(function(){  
     menuYloc = parseInt($(name).css("top").substring(0,$(name).css("top").indexOf("px")))  
     $(window).scroll(function () {   
         var offset = menuYloc+$(document).scrollTop()+"px";  
         $(name).animate({top:offset},{duration:500,queue:false});  
     });  
 });