DIV始终居中的js代码

复制代码 代码如下:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>侧边栏广告</title>
<style type="text/css">
#show { width:100px; height:80px; background:#0f0; position:fixed; _position:absolute; right:0px; top:0px;}
</style>
<script type="text/javascript">
window.onscroll = window.onresize = window.onload = function(){

var oDiv = document.getElementById("show");
var sTop = document.documentElement.scrollTop || document.body.scrollTop;
var cHeight= document.documentElement.clientHeight || document.body.clientHeight;
var mid = (cHeight - oDiv.offsetHeight) / 2;
// oDiv.style.top = parseInt(sTop + mid) + "px"; //理论上应该只设这句就可以居中吧

//实际上的 各大浏览器只认识下面这if判断
if(navigator.appVersion.indexOf("MSIE 6")> -1){
oDiv.style.top = parseInt(sTop + mid) + "px";
}else{
oDiv.style.top =mid + "px";
}
}