DIV+CSS 三栏布局实例代码

.right,.left{height:300px;width:200px;}
.right{ float:right;background:#000000;}
.left{ float:left;background:#009933;}
.main{background:#F60; height:300px;}
<div class="right">RIGHT</div>
<div class="left">LEFT</div>
<div class="main">MAIN</div>

.boxmain{float:left;margin-right:-200px;width:100%;}
.right,.left{height:300px;width:200px; z-index:1;}
.right{ position:absolute; right:0; background:#000000;}
.left{position:absolute;left:0; background:#009933;}
.main{margin-right:200px;background:#F60; height:300px;margin-left:200px;}
<div class="boxmain">
<div class="main">main</div>
</div>
<div class="left">LEFT</div>
<div class="right">RIGHT</div>