@import url(nav.css);
html,body{margin:0;padding:0;height:100%;min-height:100%;text-align:center;}
body{width:100%;margin:0 auto;max-width:980px;background:yellow;}
body > div:first-child{min-height:100%;}
header,nav,footer{width:100%;}
header{height:100px;background:#D5D5D5;}
section{width:70%;float:left;background:green;}
aside{width:30%;float:right;background:blue;}
footer{clear:both;height:50px;margin-top:-50px;background:red;}