<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Главная страница</title>
<style>
#center{
background: orange;
width: 70%;
height: 100%;
float: left;
}
#left{
background: black;
width: 15%;
height: 100%;
float: left;
}
#right{
background: black;
width: 15%;
height: 100%;
float: left;
}
</style>
</head>
<body>
<div id="left">лево</div>
<div id="center">центр</div>
<div id="right">право</div>
</body>
</html>