三列等高布局

　　　　<div class="box clearfix">
		<div class="container3">
			<div class="container2">
				<div class="container1">
					<div class="col1">
						<p>col1col1col1col1</p>
						<p>col1col1col1col1</p>
						<p>col1col1col1col1</p>
					</div>
					<div class="col2">
						<p>col2 col2 col2 col2 col2 </p>
						<p>col2 col2 col2 col2 col2 </p>
						<p>col2 col2 col2 col2 col2 </p>
					</div>
					<div class="col3">
						<p>col3 col3 col3 col3 col3 col3</p>
						<p>col3 col3 col3 col3 col3 col3</p>
						<p>col3 col3 col3 col3 col3 col3</p>
						<p>col3 col3 col3 col3 col3 col3</p>
						<p>col3 col3 col3 col3 col3 col3</p>
					</div>
				</div>
			</div>
		</div>
	</div>

.clearfix:before,.clearfix:after{content:" ";display:table;}.clearfix:after{clear:both;}.clearfix{*zoom:1;}
.box{width:1000px;margin:0 auto;}
.container3{width:100%;float:left;background:green;overflow:hidden;position:relative;}
.container2{width:100%;float:left;background:yellow;position:relative;right:300px; /*等于col3的宽度*/}
.container1{width:100%;float:left;background:orange;position:relative;right:400px;/*等于col2的宽度*/}
		
.col1{width:300px;float:left;position:relative;left:700px;}
.col2{width:400px;float:left;position:relative;left:700px;}
.col3{width:300px;float:left;position:relative;left:700px;}