!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh" lang="zh">
<head profile="http://www.w3.org/2000/08/w3c-synd/#">
<meta http-equiv="content-language" content="zh-cn" />
<meta http-equiv="content-type" content="text/html;charset=gb2312" />
<title>blueidea</title>
<style type="text/css">
<!--
body {font-size:12px;
margin:0;
padding:0;}
#head { position:relative;
margin: auto; /*---页面居中的写法------*/
900px; /*----加了宽度效果就看得出了，原来是全屏的-----*/
}
.vb {
float:left;
height: 200px;
300px;
background:#CC0000;
}
.bb {float:left;
height: 200px;
300px;
background:#3300CC;
}
.vv {float:left;
height: 200px;
300px;
background:#FF9900;
-->
</style>
</head>
<body>
<div id="head">
<div class="vb">此处显示 class "vb" 的内容</div>
<div class="bb">此处显示 class "bb" 的内容</div>
<div class="vv">此处显示 class "vv" 的内容</div>
</div>
</body>
</html>