使DIV始终居于屏幕中间的方法
方法1：

<!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>

<TITLE>随滚动条移动的层 - 飘逸online-http://www.ie521.com </TITLE>

<META HTTP-EQUIV="Content-Type" CONTENT="text/html" charset="gb2312">

<META NAME="Author" CONTENT="haiwa">

<META NAME="homepage" CONTENT="www.51windows.net">

</HEAD>

<style>

<!--

.div{

    position: absolute;

    border: 2px solid red;

    background-color: #EFEFEF;

    line-height:90px;

    font-size:12px;

    z-index:1000;

}

-->

</style>

<BODY>

<div id="Javascript.Div1" class="div" style="width: 240px; height:90px" align="center">正中...</div>

<SCRIPT LANGUAGE="JavaScript">

function sc1(){

    document.getElementById("Javascript.Div1").style.top=(document.documentElement.scrollTop+(document.documentElement.clientHeight-document.getElementById("Javascript.Div1").offsetHeight)/2)+"px";

    document.getElementById("Javascript.Div1").style.left=(document.documentElement.scrollLeft+(document.documentElement.clientWidth-document.getElementById("Javascript.Div1").offsetWidth)/2)+"px";

}

</SCRIPT>

<div id="Javascript.Div2" class="div" style="width: 240px; height:90px" align="center">左上...</div>

<SCRIPT LANGUAGE="JavaScript">

function sc2(){

    document.getElementById("Javascript.Div2").style.top=(document.documentElement.scrollTop)+"px";

    document.getElementById("Javascript.Div2").style.left=(document.documentElement.scrollLeft)+"px";

}

</SCRIPT><div id="Javascript.Div3" class="div" style="width: 240px; height:90px" align="center">左下...</div>

<SCRIPT LANGUAGE="JavaScript">

function sc3(){

    document.getElementById("Javascript.Div3").style.top=(document.documentElement.scrollTop+document.documentElement.clientHeight-document.getElementById("Javascript.Div3").offsetHeight)+"px";

    document.getElementById("Javascript.Div3").style.left=(document.documentElement.scrollLeft)+"px";

}

</SCRIPT><div id="Javascript.Div4" class="div" style="width: 240px; height:90px" align="center">右上...</div>

<SCRIPT LANGUAGE="JavaScript">

function sc4(){

    document.getElementById("Javascript.Div4").style.top=(document.documentElement.scrollTop)+"px";

    document.getElementById("Javascript.Div4").style.left=(document.documentElement.scrollLeft+document.documentElement.clientWidth-document.getElementById("Javascript.Div4").offsetWidth)+"px";

}

</SCRIPT><div id="Javascript.Div5" class="div" style="width: 240px; height:90px" align="center">右下...</div>

<SCRIPT LANGUAGE="JavaScript">

function sc5(){

    document.getElementById("Javascript.Div5").style.top=(document.documentElement.scrollTop+document.documentElement.clientHeight-document.getElementById("Javascript.Div5").offsetHeight)+"px";

    document.getElementById("Javascript.Div5").style.left=(document.documentElement.scrollLeft+document.documentElement.clientWidth-document.getElementById("Javascript.Div5").offsetWidth)+"px";

}

</SCRIPT>
<SCRIPT LANGUAGE="JavaScript">

<!--

function scall(){

    sc1();sc2();sc3();sc4();sc5();

}

window.onscroll=scall;

window.onresize=scall;

window.onload=scall;

//-->

</SCRIPT>

<div style="position: absolute; top: 0px; left: 0px; width: 10000px; height: 4000px;"></div>

</BODY>

</HTML>

方法2：

<!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"; lang="gb2312">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />

<meta http-equiv="Content-Language" content="zh-cn" />

<meta content="all" name="robots" />

<meta name="Author" content="huobazi@aspxboy.com ,ｻ銧ﾐﾗﾓ" />

<meta name="Copyright" content="www.AspxBoy.Com,ﾗﾔﾓﾉｰ;貶ｨ,ﾈﾎﾒ籏ｪﾔﾘ." />

<meta name="Description" content="www.AspxBoy.Com" />

<meta name="Keywords" content="www.AspxBoy.Com,ｻ;銧ﾐﾗﾓ,huobazi" />

<title> New New Document</title></head>

<body>

<iframe frameborder="0" src="about:blank"style="border:0px;position:absolute;z-index:9;left:0px;top:0px;width:expression(this.offsetParent.scrollWidth);height:expression(this.offsetParent.scrollHeight);filter:progid:DXImageTransform.Microsoft.Alpha(Opacity=75, FinishOpacity=0, Style=0, StartX=0, FinishX=100, StartY=0, FinishY=100);"></iframe>
<div style="position:absolute;z-index:10;left:expression((this.offsetParent.clientWidth/2)-(this.clientWidth/2)+this.offsetParent.scrollLeft);top:expression((this.offsetParent.clientHeight/2)-(this.clientHeight/2)+this.offsetParent.scrollTop);">Please Wait...<br /><img src="/_images/statusbar.gif" /></div>

</body></html>



方法三：

<div id="divObjection" style="display:none; z-index: 100; left: 25%; right:25%; position: absolute; text-align: center; width: 50%; height: 120px; border-right: #009900 1px solid; border-top: #009900 1px solid; border-left: #009900 1px solid; border-bottom: #009900 1px solid; background-color: #f9fff6;"></div>