Untitled

<!doctype html>
<html>
<head>
	<title>css</title>
<style>
.wrapper{
	text-align:center;
	width:300px;
	border:1px solid black;
	margin:0 auto;
	background:#ddd;
}
nav{
	border-bottom:1px solid black;
	border-top:1px solid black;
}
main section{
	width:30%;
}
main aside{
	width:30%;
}
footer{
	border-top:1px solid black;
}
main*{
	float:left;
}
main{
	overflow:hidden;
}
</style>
</head>
<body>
	<div class="wrapper">
<header>Header</header>
<nav>Menu</nav>
<main>
	<section>Content</section>
	<aside>Sidebar</aside>
</main>
<footer>Footer</footer>
</body>
</div>