css 层居中
<html>
<head><title>..</title></head>
<style>
body {TEXT-ALIGN: center;}
#wrappera { width:1006px; height:300px; margin:0px auto; background-color:#ffcc33}
#wrapperb{clear: both; margin: 0 auto 0px; min-height: 300px;padding: 0;width:
1006px;overflow:hidden; background-color:#ffcc33}
</style>
<body>
<div id="containera">
<div id=wrappera>123</div>
<br>
<div id=wrapperb>234</div>
</div>
</body>
</html>
