Document should not have more than one main landmark
How to Fix the Problem
Ensure there is a navigation point to the primary content of the page. If the
iframe elements, each
contain either no main landmarks or just one.
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 HTML 5 and ARIA landmarks
to ensure all content is contained within a navigational region. In HTML5, you
should use elements like
footer. Their ARIA counterparts are
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. Landmarks provide 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 can’t replace skip navigation links altogether.
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.
Why it Matters
Navigating a web page is far simpler for screen reader users if all of the content splits between one or more high-level sections. Content outside of these sections is difficult to find, and its purpose may be unclear.
HTML has historically lacked some key semantic markers, such as the ability to designate sections of the page as the header, navigation, main content, and footer. Using both HTML5 elements and ARIA landmarks in the same element is considered a best practice, but the future will favor HTML regions as browser support increases.
It is a best practice to ensure that there is only one main landmark to
navigate to the primary content of the page and that if the page contains
iframe elements, each should either contain no landmarks, or just
a single landmark.
The Algorithm (in simple terms)
Ensures the document has at most one main landmark.