adleft.style.top=adtop+(document.documentElement.scrollTop || document.body.scrollTop)+"px";
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>仿js对联广告 - www.jb200.com</title>
<style>
body{margin:0; padding:0}
#adleft,#adright{
width:30px;
height:100px;
padding:20px;
font:14px/20px arial;
text-align:center;
background:#06c;
position:absolute;
cursor:pointer;
color:#fff
}
#adleft{left:0; top:150px; }
#adright{right:0; top:150px;}
</style>
<script>
window.onload = function(){
var adleft = document.getElementById("adleft");
var adright = document.getElementById("adright");
var adtop = adleft.offsetTop;
window.onscroll = function(){
adleft.style.top = adtop + (document.documentElement.scrollTop || document.body.scrollTop) +"px";
adright.style.top = adtop + (document.documentElement.scrollTop || document.body.scrollTop) +"px";
}
}
</script>
</head>
<body style="height:2000px;">
<h1>左右广告</h1>
<div id="adleft">左边广告</div>
<div id="adright">右边广告</div>
</body>
</html>
