Explanation
To center using CSS, specify auto for left/right margin. However, in IE6 you cannot center using this method in standard model. So, you have to center using text-align:center;.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=shift_jis">
<title>Sample</title>
<style type="text/css"><!--
p {
margin-left:auto;
margin-right:auto;
width:320px;
border:1px solid black;
padding:10px;
}
--></style>
</head>
<body>
<h1>Sample</h1>
<p>
When specifying auto, you can center.<br>
However, in IE6 you have to use text-align in quirks mode.
</p>
</body>
</html>