All content should be contained in a landmark region:
banner (top level)
complementary
contentinfo (top level)
main (top level)
navigation
region (sub sections and unique content)
search
Must use labels when a landmark region of the same type is used more than once
Should not nest landmark regions of the same type
Usability of landmarks is affected by the number of landmark regions on a page. A rule of thumb is to have between 4-10 landmarks on a page to make it faster for screen reader users so rebiew them, although more complex pages may require more landmarks.