<!DOCTYPE html>
<html>
<head>
<style>
div
{
width:350px;
height:100px;
border:1px solid black;
/* Firefox */
display:-moz-box;
-moz-box-pack:center;
-moz-box-align:center;
/* Safari, Chrome, and Opera */
display:-webkit-box;
-webkit-box-pack:center;
-webkit-box-align:center;
/* W3C */
display:box;
box-pack:center;
box-align:center;
}
</style>
</head>
<body>
<div>
<span>我是居中对齐的。</span>
</div>
</body>
</html>
