<body>
<header role="banner">
[...]
</header>
<main role="main">
<article>
<header>
[...]
</header>
[...]
<footer>
[...]
</footer>
</article>
</main>
<footer role="contentinfo">
[...]
</footer>
</body>
Sometimes you need extra divs to achieve your visual design. An inner
div on the body could be used to set a centred, fixed width column for the page.
<body>
<div class="inner">
<header role="banner">
[...]
</header>
<main role="main">
<article>
<header>
[...]
</header>
[...]
<footer>
[...]
</footer>
</article>
</main>
<footer role="contentinfo">
[...]
</footer>
</div>
</body>
Adding inner divs to the parent sectioning elements allows you to style and centre each one individually.
<body>
<header role="banner">
<div class="inner">
[...]
</div>
</header>
<main role="main">
<div class="inner">
<article>
<header>
[...]
</header>
[...]
<footer>
[...]
</footer>
</article>
</div>
</main>
<footer role="contentinfo">
<div class="inner">
[...]
</div>
</footer>
</body>
Source: http://www.creativebloq.com/html5/5-html5-and-aria-design-patterns-7133753