div悬浮

span style="color: #0000ff;">PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">


<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title></title>
<style type="text/css">
</style>


<!--z-index 属性设置元素的堆叠顺序。拥有更高堆叠顺序的元素总是会处于堆叠顺序较低的元素的前面。z-index 仅能在定位元素上奏效（例如 position:absolute;）！-->
<div style="position:relative; width:500px; height:500px;">
<div style="position:absolute; z-index:2; width:300px; height:300px; left:0px; top:0px; background-color:red;"></div>
<div style="position:absolute; z-index:3; width:200px; height:200px; left:0px; top:0px;background-color:green;">></div>
</div>