JS实现自适应高度的对联广告代码

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>简洁对联广告代码</title>
<script language="JavaScript" type="text/javascript">
lastScrollY=0;
function heartBeat(){ 
var diffY;
if (document.documentElement && document.documentElement.scrollTop)
diffY = document.documentElement.scrollTop;
else if (document.body)
diffY = document.body.scrollTop
else
{/*Netscape stuff*/}
//alert(diffY);
percent=.1*(diffY-lastScrollY); 
if(percent>0)percent=Math.ceil(percent); 
else percent=Math.floor(percent); 
document.getElementById("lovexin12").style.top=parseInt(document.getElementById
("lovexin12").style.top)+percent+"px";
document.getElementById("lovexin14").style.top=parseInt(document.getElementById
("lovexin12").style.top)+percent+"px";
lastScrollY=lastScrollY+percent; 
//alert(lastScrollY);
}
suspendcode12="<DIV id=\"lovexin12\" style='left:2px;POSITION:absolute;TOP:120px;'>ad1</div>"
suspendcode14="<DIV id=\"lovexin14\" style='right:2px;POSITION:absolute;TOP:120px;'>ad2</div>"
document.write(suspendcode12); 
document.write(suspendcode14); 
window.setInterval("heartBeat()",1);
</script>
<style type="text/css">
<!--
#lovexin12,#lovexin14{
width:100px;
height:230px;
background-color:yellow;
border:2px solid red;
}
html,body{
height:800px;
}
#mm{
height:800px;
}
-->
</style>
</head>
<body>
<div id="mm">
基于JS+CSS+DIV的网页对联广告代码
</div>
</body>
</html>