Usability: global links where users most expect to see them
Semantic logic: the collection of global links should be marked up as a list, because, well, it is a list
Accessibility: the list format of links appears early in the code listing, where it should be
Search visibility: a collection of your major navigation keywords, linked and at the top of the code listing, is ideal for search engine optimization
Tabs are another widely used, easily understood convention for global navigation. The best way to implement tabs is to style an ordinary html list with a more elaborate css treatment to form the “tab” graphic around each link. Be sure you get the graphic details right: the selected tab should be graphically unambiguous, and the remaining tabs should clearly be behind the selected tab. This type of “you are here” marker is essential in orienting users within the site. Tabs can also be used to implement a two-tiered navigation scheme, in which a secondary horizontal list of links appears under the selected tab, again as a simple html list with css styling, to keep things semantic, accessible, and search visible (fig. 6.2).