关于广告浮动问题？

[ykklv]

我在首页里添加了两边浮动的广告，它怎么不随滚动条上下滚动呢？代码是网上找的，我把
<script language=JavaScript src="ad-02.js"></script>放在<body>下面的，广告图片可以显示出来。什么原因呢？大家有没有好的可以浮动的广告代码,给我共享，只要能用就给分。[e-mail]

[cnhxjtoa]

<div id="ad" style="position:absolute">
<a href= target="_blank">
<img src="你的图片.gif" border="0">
</a></div>
<script>
var x = 50,y = 60
var xin = true, yin = true
var step = 1
var delay = 10
var obj=document.getElementById("ad")
function floatAD() {
var L=T=0
var R= document.body.clientWidth-obj.offsetWidth
var B = document.body.clientHeight-obj.offsetHeight
obj.style.left = x + document.body.scrollLeft
obj.style.top = y + document.body.scrollTop
x = x + step*(xin?1:-1)
if (x < L) { xin = true; x = L}
if (x > R){ xin = false; x = R}
y = y + step*(yin?1:-1)
if (y < T) { yin = true; y = T }
if (y > B) { yin = false; y = B }
}
var itl= setInterval("floatAD()", delay)
obj.onmouseover=function(){clearInterval(itl)}
obj.onmouseout=function(){itl=setInterval("floatAD()", delay)}
</script>