Main landmark must not be contained in another landmark

Ensure the main landmark is not contained in another landmark.

Ensure all content is contained within a landmark region, designated with HTML5 landmark elements and/or ARIA landmark regions.

It is a best practice to use both HTML5 and ARIA landmarks to ensure all content is contained within a navigational region. In HTML5, you should use elements like <header>, <nav>, <main>, and <footer>. Their ARIA counterparts are role="banner", role="navigation", role="main", and role="contentinfo", in that order. By using both HTML5 and ARIA markup, you make the webpage more robust and functional no matter what screen reader technology is used.

Once added, screen reader users can navigate to a section based on its ARIA landmark or HTML element. The contentinfo landmark provides a simple replacement for a skip navigation link, though the replacement is only useful for users of screen readers. Sighted users or users of screen enlargers wouldn’t get much benefit from the addition, so it the contentinfo landmark does not replace skip navigation links altogether.

Example

A simplified web page, stripped down to just the bare landmark essentials, might look something like this:

<header role="banner">
   <p>Put company logo, etc. here.</p>
</header>
<nav role="navigation">
   <ul>
      <li>Put navigation here</li>
   </ul>
</nav>
<main role="main">
   <p>Put main content here.</p>
</main>
<footer role="contentinfo">
   <p>Put copyright, etc. here.</p>
</footer>

The markup for regions and roles is redundant, but this is a transition period, and the above markup is the most robust.