<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="utf-8"/>
<title>CSS Test Page</title>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
.cent{
background:#0CF; height:200px; width:100px;
}
.cs{
width:100px;
height:200px;
background:#F09;
top:0px;
position:absolute;
opacity: 0;
display: block;
font-size: 12px;
transition: 0.3s;
-webkit-transition: .5s;
-moz-transition: .5s;
}
.cent:hover .cs{
color: #656e73;
opacity: 1;
}
</style>
</head>
<body>
<div class="cent">
This is the cent div
<div class="cs">
<p>this is a cs div</p>
</div>
</div>
</body>
</html>
原文：http://www.cnblogs.com/Lily-L/p/6959782.html