<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>透明层-弹出层</title>
<style>
*{margin:0;padding:0;}
.main{width:100%; height:1000px;}
.div1{
top:0;
left:0;
width:100%;
height:1000px;
position:absolute;
z-index:10;
}
.div2{
width:100%;
height:1000px;
z-index:-1;
position:absolute;
/**透明层*/
background:#000000;
filter:alpha(opacity=70);
-moz-opacity:0.7;
-khtml-opacity: 0.7;
opacity: 0.7;
}
.div3{
margin-left:100px;
width:100px;
height:200px;
background:yellow;
}
</style>
</head>
<body >
<div class="main">dsadd</div>
<div class="div1">
<!-- 因为子元素会继承父元素的透明层opacity 所以定义一个空div作为透明层 -->
<div class="div2"></div>
<div class="div3">wqeqwe</div>
</div>
</body>
</html>
原文：http://www.cnblogs.com/jalja/p/4174568.html