div浮层，滚动条移动，保持位置不变的4种方法

div在顶部不变、滚动条滚动，div还是在顶部！

直接上传源码了：

方法一：

<!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>div浮层，滚动条移动，保持位置不变</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
body{background-image:url(about:blank);background-attachment:fixed;}
#float{344px;height:34px;border:1px solid #C0DBF8;position:absolute;top:0px;}
</style>
</head>
<body>
<div id="float" >ddd</div>
</body>
<script type="text/javascript">
var IO=document.getElementById('float'),Y=IO,H=0,IE6;
IE6=window.ActiveXObject&&!window.XMLHttpRequest;
while(Y){H+=Y.offsetTop;Y=Y.offsetParent};
if(IE6)
IO.style.cssText="position:absolute;top:(this.fix?(document.documentElement.scrollTop-(this.javascript||"+H+")):0)";
window.onscroll=function (){
var d=document,s=Math.max(d.documentElement.scrollTop,document.body.scrollTop);
if(s>H&&IO.fix||s<=H&&!IO.fix)return;
if(!IE6)IO.style.position=IO.fix?"":"fixed";
IO.fix=!IO.fix;
};
try{document.execCommand("BackgroundImageCache",false,true)}catch(e){};
</script>
</html>

<!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>div浮层，滚动条移动，保持位置不变</title> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<style type="text/css"> 
body{background-image:url(about:blank);background-attachment:fixed;}
#float{344px;height:34px;border:1px solid #C0DBF8;position:absolute;top:0px;}
</style> 
</head> 
<body>
<div id="float" >ddd</div>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
</body> 
<script type="text/javascript">
var IO=document.getElementById('float'),Y=IO,H=0,IE6;
IE6=window.ActiveXObject&&!window.XMLHttpRequest;
while(Y){H+=Y.offsetTop;Y=Y.offsetParent};
if(IE6)
    IO.style.cssText="position:absolute;top:(this.fix?(document.documentElement.scrollTop-(this.javascript||"+H+")):0)";
window.onscroll=function (){
    var d=document,s=Math.max(d.documentElement.scrollTop,document.body.scrollTop);
    if(s>H&&IO.fix||s<=H&&!IO.fix)return;
    if(!IE6)IO.style.position=IO.fix?"":"fixed";        
    IO.fix=!IO.fix;
};
try{document.execCommand("BackgroundImageCache",false,true)}catch(e){};
</script> 
</html>

方法二：

[html] view plain copy print ?

<body topmargin="0" bottommargin="0" leftmargin="0" rightmargin="0" style="overflow: hidden;">
<div style=" 100%; height: 100%; overflow: scroll;">
</div>
<div style="border: 1px red solid; 300px; height: 300px;margin:-150px 0 0 -150px; position: absolute; left: 50%; top: 50%;">
居中的层
</div>
</body>

<body topmargin="0" bottommargin="0" leftmargin="0" rightmargin="0" style="overflow: hidden;">
 <!-- div来实现 -->
 <div style=" 100%; height: 100%; overflow: scroll;">
  <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
  <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
  <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
  <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
 </div>
<div style="border: 1px red solid;  300px; height: 300px;margin:-150px 0 0 -150px; position: absolute; left: 50%; top: 50%;">
  居中的层
 </div>
</body>

方法三：

[html] view plain copy print ?

<body topmargin="0" bottommargin="0" leftmargin="0" rightmargin="0" style="overflow: hidden;">
<iframe src="http://www.csdn.net/" width="100%" height="100%" frameborder="0"></iframe>
<div style="border: 1px red solid; 300px; height: 300px;margin:-150px 0 0 -150px; position: absolute; left: 50%; top: 50%;">
居中的层
</div>
</body>

<body topmargin="0" bottommargin="0" leftmargin="0" rightmargin="0" style="overflow: hidden;">
 <!-- iframe来实现  -->
 <iframe src="http://www.csdn.net/" width="100%" height="100%" frameborder="0"></iframe>
<div style="border: 1px red solid;  300px; height: 300px;margin:-150px 0 0 -150px; position: absolute; left: 50%; top: 50%;">
 居中的层
 </div>
</body>

方法四：[采用css来居中]

[html] view plain copy print ?

<style type="text/css">
<!--
html,body {height:100%; margin:0px; font-size:12px;}
.mydiv {
background-color: #f9fff6;
border: 1px solid #009900;
text-align: center;
line-height: 25px;
font-size: 13px;
font-weight: bold;
z-index:99;
300px;
height: 50px;
left:50%;/*FF IE7*/
top:50%;/*FF IE7*/
margin-left:-150px!important;/*FF IE7 half of its width */
margin-top:-60px!important;/*FF IE7 half of its height*/
margin-top:0px;
position:fixed!important;/*FF IE7*/
position:absolute;/*IE6*/
_top: expression(eval(document.compatMode &&
document.compatMode=='CSS1Compat') ?
documentElement.scrollTop + (document.documentElement.clientHeight-this.offsetHeight)/2 :/*IE6*/
document.body.scrollTop + (document.body.clientHeight - this.clientHeight)/2);/*IE5 IE5.5*/
}
-->
</style>
<script language="javascript" type="text/javascript">
function showDiv(){
document.getElementById('popDiv').style.display='block';
}
window.onload=function(){
showDiv();
}
</script>
<!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=gb2312" />
<title>始终在中间DIV (支持IE FF)</title>
</head>
<body>
<div id="popDiv" class="mydiv" style="display:none;">始终在中间
</div>
</body>
</html>

<style type="text/css">
<!--
html,body {height:100%; margin:0px; font-size:12px;}

.mydiv {
background-color: #f9fff6;
border: 1px solid #009900;
text-align: center;
line-height: 25px;
font-size: 13px;
font-weight: bold;
z-index:99;
 300px;
height: 50px;
left:50%;/*FF IE7*/
top:50%;/*FF IE7*/

margin-left:-150px!important;/*FF IE7 half of its width */
margin-top:-60px!important;/*FF IE7 half of its height*/

margin-top:0px;
position:fixed!important;/*FF IE7*/
position:absolute;/*IE6*/

_top:       expression(eval(document.compatMode &&
            document.compatMode=='CSS1Compat') ?
            documentElement.scrollTop + (document.documentElement.clientHeight-this.offsetHeight)/2 :/*IE6*/
            document.body.scrollTop + (document.body.clientHeight - this.clientHeight)/2);/*IE5 IE5.5*/

}
--> 
</style>
<script language="javascript" type="text/javascript">
function showDiv(){

document.getElementById('popDiv').style.display='block';

}
window.onload=function(){
    showDiv();
}
</script>
<!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=gb2312" />
<title>始终在中间DIV (支持IE FF)</title>

</head>

<body>
<div id="popDiv" class="mydiv" style="display:none;">始终在中间<br/>
</div>
<br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>
</body>
</html>