Document should have one main landmark

Translation & meaning:

The page should be marked with a main landmark.

It is best practice to use both HTML 5 and ARIA landmarks to ensure that all content is within different landmarks.

In HTML5, you should use elements such as header, nav, main, and footer.

Their equivalents in ARIA are role="banner", role="navigation", role="main" and role="contentinfo", in that order.

By using both HTML5 and ARIA markup, you make the web page more robust and functional regardless of the screen reader technology used.