puedes usar esto
<html>
<head>
<style>
html,body{margin:0;padding:0}
body{font: 76% arial,sans-serif}
p{margin:0 10px 10px}
a{display:block;color: #981793;padding:10px}
div#header h1{height:80px;line-height:80px;margin:0;
padding-left:10px;background: #EEE;color: #79B30B}
div#content p{line-height:1.4}
div#left{background:#B9CAFF}
div#right{background:#FF8539}
div#footer{background: #333;color: #FFF}
div#footer p{margin:0;padding:5px 10px}
div#wrapper{float:left;width:100%}
div#content{margin: 0 25%}
div#left{float:left;width:25%;margin-left:-100%}
div#right{float:left;width:25%;margin-left:-25%}
div#footer{clear:left;width:100%}
</style>
</head>
<body>
<div id="container">
<div id="header"><h1>Header</h1></div>
<div id="wrapper">
<div id="content">
<p>contenido</p>
</div>
</div>
<div id="left">
<p>left </p>
</div>
<div id="right">
<p>right </p>
</div>
<div id="footer"><p>footer</p></div>
</div>
</body>
</html>