I'm not sure if many people besides me make use of the tabindex feature, which means that one can navigate through the page by just clicking the tab key, but I noted that it doesn't really make sense. The first tab index goes into the search form, which is good, then it jumps to all collapsible menus (not the menu items), and then to the page. It should probably be: search form, navigation menu (first uncollapsed, namespace tabs and then the page content. Otherwise, it takes to "scroll" through the whole page content to get to the navigation. Tested in the Vector skin of http://en.wikipedia.org/wiki/Main_Page, not sure about other skins.