- Go to a SharePoint page using a default master page, your own or a site such as http://www.wssdemo.com/.
- Click as close to the top left corner of the page as possible (just in front of the crumb trail)
- Press Tab - you should now see "Turn off more accessible mode" (if this is does not work, experiment with several tabs or shift-tabs)
What this is supposed to do is change how some navigation controls work. For example, if you are on your own site that has a Welcome menu, click the menu. Instead of a dropdown you will get a new window with all of the choices displayed. If you are testing this with the WSSDEMO site then display a page with a list or library that has an Action menu. Then turn "more accessible" on and click the Action menu. (you may get a warning from your popup blocker)
For more information on accessibility see: Microsoft Active Accessibility (MSAA).
For a great blog article on MOSS accessibility go here: http://www.21apps.com/2007/03/sharepoint-accessibility-is-moss-2007_4974.html