用CSS属性里面的"z-index:(数值)“,数值可为负数,但是z-index必须配合"position"定位才可以使用,不然是没有效果的。例如:(z-index数值越大的越在上面。)<!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>无标题文档</title>
<style type="text/css">
#AAA{
position:absolute;
top:50px;
left:150px;
width:150px;
cursor:pointer;
height:150px;
z-index:4;
background-color:#F00;
}
#BBB{
position:absolute;
top:80px;
left:180px;
width:150px;
height:150px;
cursor:pointer;
z-index:5;
background-color:#0F0;
}
</style>
</head><body>
<div id="AAA" onclick="this.style.zIndex='5';document.getElementById('BBB').style.zIndex='4';">AAA <!--点击这个层它的z-index变为4,显示到下面--></div>
<div id="BBB" onclick="this.style.zIndex='4';document.getElementById('BBB').style.zIndex='5';">BBB <!--点击这个层它的z-index变为5,显示到上面--></div>
</body>
</html>