This may or may not be what you're looking for. It'll center it though.
Code:
body { background-color: #999999; font-size:12px; font-family:Verdana, Arial, Helvetica, sans-serif;
}
div#outer { width: 80%; background-color:#FFFFFF; margin-top: 50px; margin-bottom: 50px; margin-left: auto; margin-right: auto; padding: 0px; border: thin solid #000000;
}
div#header { padding: 15px; margin: 0px; text-align: center;
}
div#nav { width: 25%; padding: 10px; margin-top: 1px; float: left;
}
div#main { margin-left: 30%; margin-top: 1px; padding: 10px;
}
div#footer { padding: 15px; margin: 0px; border-top: thin solid #000000;
}