试试这样?<!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>test</title>
<style type="text/css">
.test{position:absolute;clip:rect(20px 150px 70px 0px)}
</style>
</head>
<body>
<a href="http://www.google.cn"><img src="http://www.google.cn/intl/zh-CN/images/logo_cn.gif" class="test"/></a>
</body>
</html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>test</title>
<style type="text/css">
.test{position:absolute;clip:rect(20px 150px 70px 0px)}
</style>
</head>
<body>
<a href="http://www.google.cn"><img src="http://www.google.cn/intl/zh-CN/images/logo_cn.gif" class="test"/></a>
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<style type="text/css">
div#bigBox{
background-image: url(http://t2.baidu.com/it/u=2260984201,3807021784&fm=3&gp=41.jpg);
border:solid;
width:100%;
height:100%;
}
div#firstBox{
border:solid;
width:100%;
height:32%;
}
div#secondBox{
border:solid;
width:100%;
height:36%;
}div#thirdBox{
border:solid;
width:100%;
height:32%;
}
</style>
<script type="text/javascript">
function Onclick(url){
window.open(url);
}
function myClick(){
document.getElementById('firstBox').style.backgroundImage = "url(http://avatar.profile.csdn.net/E/A/4/2_varlj.jpg)";
document.getElementById('thirdBox').style.backgroundImage = "url(http://avatar.profile.csdn.net/E/A/4/2_varlj.jpg)";
}
</script>
</HEAD> <BODY>
<div id="bigBox">
<div id="firstBox"></div>
<div id="secondBox" align="center">
<input type="button" id="baidu" height=10px onclick="Onclick('http://www.baidu.com')" value="去百度"/><br/>
<input type="button" id="baidu" height=10px onclick="myClick()" value="改变"/><br/>
</div>
<div id="thirdBox">ddd</div> </div>
</BODY>
</HTML>
document.getElementById('bigBox').style.backgroundImage = "url(http://avatar.profile.csdn.net/E/A/4/2_varlj.jpg)";
}