<!DOCTYPE html>
<!--
有限宽度带居中布局：
<style>
*{margin:0;padding:0;list-style:none;}
.zong{background:#ccc;}
.zong .header{height:100px;background:#f00;}
.zong .body{background:#0f0;}
.zong .body .content{width:450px;height:500px;background:#00f;}
.zong .body .sidebar{width:150px;height:600px;background:#ff0;}
.zong .footer{height:100px;background:#0ff;}
/*布局*/
.zong{width:600px;margin:0 auto;}
.content{float:left;}
.sidebar{float:left;}
.footer{clear:both;}
.clearfix:after{content:"\200B";display:block;height:0;clear:both;}
.clearfix{*zoom:1;}/*IE/7/6*/
</style>
<div class="zong">
<div class="header"></div>
<div class="body clearfix">
<div class="content"></div>
<div class="sidebar"></div>
</div>
<div class="footer"></div>
</div>
-->
无限宽度带居中布局：
<style>
*{margin:0;padding:0;list-style:none;}
.zong2{background:#ccc;}
.zong2 .header{height:100px;background:#f00;}
.zong2 .body{background:#0f0;}
.zong2 .body .content{width:450px;height:500px;background:#00f;}
.zong2 .body .sidebar{width:150px;height:600px;background:#ff0;}
.zong2 .footer{height:100px;background:#0ff;}
/*布局*/
.content{float:left;}
.sidebar{float:left;}
.footer{clear:both;}
/*body居中*/
.body{width:600px;margin:0 auto;}
/*header/footer内div设宽，居中，外div不设宽，背景*/
.zong2{min-width:600px;}/*页面缩小后仍然正常*/
.header div{width:600px;margin:0 auto;}
.footer div{width:600px;margin:0 auto;}
</style>
<div class="zong2">
<div class="header">
<div>header headerheade rheaderh eaderh eaderh ead erheader headerhe aderh eaderh eaderh ead erheade rhe aderhea derhead erhead erheaderh eade rheader header</div>
</div>
<div class="body">
<div class="content"></div>
<div class="sidebar"></div>
</div>
<div class="footer">
<div>dfooterfoo terfooterfooterfooterfooterfoo terfooter footer footerfooterfooterfooterfooterfooterf ooter footerfoote rfooterf ooterfooter foote rfoot erfooterf ooterfooter footer</div>
</div>
</div>
<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
<br>