Assign a complementary landmark role to supporting content
Make sure supporting content is identified using the complementary landmark role
When trying to organize content in a way that makes sense, authors often rely on descriptive ID values to describe regions of their page. Hence, sidebars often end up being assigned ID values such as “leftColumn”, or “supportingInfo”. While this denomination makes sense as authors build the site, it conveys no meaning to assistive technologies as users try to access this information. The complementary landmark role is intended to fix this, by programmatically defining regions that usually contain information that is not considered main content, but do complement the main point. Thanks to the complementary landmarks role, users can easily jump to such sections and discover what they are about.
To do this, simply make sure each region of content not directly tied in to the main content is assigned a “complementary” landmark role. Complementary content should be relevant to the main content – if it is completely separable, a more general role should be used instead. To provide additional confirmation about the region’s purpose, consider assigning an aria-label attribute with a value describing what this content is about, or even wrap the region [...]