var name = "#winkelwagen";
    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:50,queue:false});
        });
    });