Hola seria algo asi:
Código HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Documento sin título</title>
<style type="text/css">
.container {
width: 80%;
max-width: 900px;
min-width: 780px;
background-color: #FFF;
margin: 0 auto;
overflow: hidden;
}
.left {
float: left;
width: 20%;
background-color: #93A5C4;
padding: 10px 0;
overflow: hidden;
}
.contenido {
padding: 10px 0;
width: 60%;
float: left;
word-wrap: break-word;
overflow: hidden;
background-color: #999;
}
.right {
float: left;
width: 20%;
background-color: #93A5C4;
padding: 10px 0;
overflow: hidden;
}
</style>
</head>
<body>
<div class="container">
<div class="left"></div>
<div class="contenido">sssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss</div>
<div class="right"></div>
</div>
</body>
</html>