在介绍完新之后又回顾<div>元素，这可能令人感到奇怪（毕竟，这些新元素通常可以替代这个元素）
<html>
<head>
<title>TODO supply a title</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<div>TODO write content</div>
<div class='wrapper'>
<header>
<h1>Yoko's kitchen</h1>
<nav>
<!-- nav content here -->
</nav>
</header>
<section class='courses'>
<!-- section content here -->
</section>
<aside>
<!--aside content here-->
</aside>
<footer>
<!-- footer content here -->
</footer>
</div><!--.wrapper-->
</body>
</html>