悬浮于页面中间的层

<SCRIPT FOR=window EVENT=onload language="javascript">
initAd();//载入页面后，调用函数initAd()
</SCRIPT>
<script language="javascript">
<!--
function initAd() {
document.all.AdLayer.style.posTop = -200;
//设置onLoad事件激发以后，广告层相对于固定后的y方向位置
document.all.AdLayer.style.visibility = 'visible'//设置层为可见
MoveLayer('AdLayer');//调用函数MoveLayer()
}
function MoveLayer(layerName) {
var x = 20;//浮动广告层固定于浏览器的x方向位置
var y = 200;//浮动广告层固定于浏览器的y方向位置
var diff = (document.documentElement.scrollTop + y - document.all.AdLayer.style.posTop)*.90;
var y = document.documentElement.scrollTop + y - diff;
eval("document.all." + layerName + ".style.posTop = y");
eval("document.all." + layerName + ".style.posright = x");//移动广告层
setTimeout("MoveLayer('AdLayer');", 0);//设置20毫秒后再调用函数MoveLayer()
}
//-->
</script>

 

 

 

 

<div id="AdLayer" style='position:absolute; width:50px; height:50px; z-index:20; visibility:hidden;; right:10px;'>

<a href="#top">顶部</a>

</div>