图片居中的css
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
<title>div里面图片垂直居中的几个例子</title>  
<style type="text/css">  
<!--    
body {   
  margin:0;padding:0   
}   
div {   
  width:500px;   
  height:500px;   
  line-height:500px;   
  border:1px solid #666;   
  overflow:hidden;   
  position:relative;   
  text-align:center;   
}   
div p {   
  position:static;   
  +position:absolute;   
  top:50%   
}   
img {   
  position:static;   
  +position:relative;   
  top:-50%;left:-50%;   
  vertical-align:middle   
}   
p:after {   
  content:".";font-size:1px;   
  visibility:hidden   
}   
-->  
</style>  
</head>  
<body>  
<div><p><img src="http://www.google.com/intl/en/images/logo.gif" /></p></div>  
</body>  
</html>  
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
<title>div里面图片垂直居中的几个例子</title>  
<style type="text/css">  
<!--    
* {margin:0;padding:0;}   
div {   
  width:500px;border:1px solid #666;   
  height:500px;   
  background:url("http://www.google.com/intl/en/images/logo.gif") center no-repeat   
}   
-->  
</style>  
</head>  
<body>  
<div></div>  
</body>  
</html>  
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>
<!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 runat="server">
    <title>未命名頁面</title>
    <script type="text/javascript">
    function setCenter(Xelement)
    {
        var parent=Xelement.parentNode;
        parent.style.position="relative";
        Xelement.style.position="absolute";
        var left=(parent.clientWidth-Xelement.clientWidth)/2;
        var top=(parent.clientHeight-Xelement.clientHeight)/2;
        Xelement.style.left=left+"px";
        Xelement.style.top=top+"px";
    }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <div id