html 5 must'aff

<!--[if lt IE 9]><script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script><![endif]-->

css

section, article, header, footer, nav, aside, hgroup, address {
display: block;
}

and the all important padding/margin clearer

*{
    margin:0;
    padding:0;
    }

how to center a layout

margin: 0 auto;