Example Code. Try It. 
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Centered Div By Wallpaperama !!!!</title>
<style type="text/css">
.main {
	width: 980px;
	padding: 10px;
	margin:0 auto;
	border: 1px solid #F00;
}
</style>
</head>
<body>
<div class="main">Centered Div By Wallpaperama !!!!</div>
</body>
</html>