HTML5 Sectioning Elements

It is important to understand that many HTML5 sectioning (e.g. main,nav, aside ...) elements by default define ARIA landmarks. If HTML5 sectioning elements are used without understanding the associated landmark structure, assistive technology users will most likely be confused and less efficient in accessing content and interacting with web pages.

HTML5 Element	Default Landmark Role
`aside`	`complementary`
`footer`	`contentinfo` when in context of the `body` element. The `footer` element is not a `contentinfo` landmark when it is a descendant of the following HTML5 sectioning elements: `article` `aside` `main` `nav` `section`
`form`	`form` when it has an accessible name using `aria-labelledby`, `aria-label` or `title` attributes
`header`	`banner` when in context of the `body` element. The `header` element is not a `banner` landmark when it is a descendant of the following HTML5 sectioning elements: `article` `aside` `main` `nav` `section`
`main`	`main`
`nav`	`navigation`
`section`	`region` when it has an accessible name using `aria-labelledby`, `aria-label` or `title` attribute