浮动只适合pc端
margin 0 auto; //左右俩边自动推进.
<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="utf-8">
<title>CSS传统布局[上]</title>
<link rel="stylesheet" type="text/css" href="style2.css">
</head>
<body><header>
header
</header><aside>
aside
</aside><section>
section
</section><footer>
footer
</footer></body>
@charset "utf-8";body {margin: 0 auto;/* 960px;*/auto;}header {height: 120px; //因为body添加了宽度,这边自适应不用添加.background-color: olive;}aside {/* 200px;*/ //两种方式下面是流布局20%;/*min- 120px;*/height: 500px;background-color: purple;float: left; //添加folat是没有宽度的,所以要加width}section {/* 760px;*/80%;height: 500px;background-color: maroon;float: right; //如果不添加float 则会重叠, 所以要添加.}footer {height: 120px;background-color: gray;clear: both; // 要么添加浮动,要么去用clear去除浮动}