只要在最外围的DIV或表格样式中设计边距为0，填充上下为0，左右为auto。
页面就自动居中里
举例：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="
http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
<!--
body{padding:0; margin:0;}
#main{padding:0; margin:0 auto; background:#3C6; width:1003px; height:100px;}
-->
</style>
</head>
<body>
<div id="main">adfafaf</div>
</body>
</html>