网页右侧的漂浮广告代码，随滚动条滚动详解编程语言

HTML代码(即需要漂浮的广告)： 
<div class="christmas_ad" style="width:155px; height:220px; position:absolute; top:250px; right:25px;"> 
<a href="javascript:void(0)" ><img src="/themes/mall/wowsai/topics/images/christmas_2012/christmasAcvance.png" border="0" /></a> 
</div> 
 
js代码：前提是必须要引入jquery文件 
<script type="text/javascript"> 
$(function(){ 
 
    $(window).scroll(function(){ 
 
        var scrollTop = document.body.scrollTop || document.documentElement.scrollTop || 0; 
 
        $(".christmas_ad").stop(); 
 
        var scrollTop2 = (scrollTop+160) - $(".christmas_ad").position().top; 
 
        if(scrollTop> 440){ 
 
            $(".christmas_ad:not(:animated)").animate({top:"+="+scrollTop2+"px"},1000); 
 
        }else{ 
 
            $(".christmas_ad").css("top",370+"px"); 
 
        } 
 
    }) 
 
})  
</script>