<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>CSS实现div居中</title>
<style>
/*外层div居中*/
#main {
position: absolute; /*极为重要*/
background-color: blue;
width:400px;
height:200px;
left:50%;
top:50%;
margin-left:-200px;
margin-top:-100px;
border:1px solid #00F;
}
#content {
position: absolute; /*极为重要*/
background-color: yellow;
width: 200px;
height: 100px;
left:50%;
top:50%;
margin-left:-100px;
margin-top:-50px;
/*div内部文字居中*/
text-align: center;
line-height:100px; /*行间距和div高度相同*/
}
</style>
<body>
<div id="main">
<div id="content">
Sun
</div>
</div>
</body>
</html>