Definition A complementary landmark is a supporting section of the document, designed to be complementary to the main content at a similar level in the DOM hierarchy, but remains meaningful when separated from the main content.
ARIA 1.1 Specification complementary landmark
Design Patterns
  • complementary landmarks should be top level landmarks (e.g. not contained within any other landmarks).
  • If the complementary content is not related to the main content, a more general role should be assigned (e.g. region).
  • If a page includes more than one complementary landmark, each should have a unique label (see Step 3 above).
  • Use the HTML5 aside element to define a complementary landmark.
  • If the HTML5 aside element technique is not being used, use a role="complementary" attribute to define a complementary landmark.
  • Each complementary landmark should have an h2 element identifying the content of the landmark.
  • If there are more than one complementary landmark on the page, use aria-labelledby to reference the h2 elements for labeling each landmark.