The ROLE tag is used in XHTML 2.0 scripting to define the "role" of an element. The Show All, Main, Secondary, Navigation, and Banner selections on the Style menu relate to this tag. The links below access sites for more information about the ROLE tag and Accessibility with Dynamic HTML pages.
The example below shows a portion of a page with and how selection of the different menu items affect the page. This example page is located at http://cita.rehab.uiuc.edu/mozilla/ts-test-page-role.php.