The spry menu bar as autogenerated by Dreamweaver (CS4/5/6) (all defaults maintained)
According to the API you can enable keyboard navigation by changing the boolean value enableKeyboardNavigation in the list of parameters as such:
var MenuBar1 = new Spry.Widget.MenuBar("MenuBar1", {imgRight:"SpryAssets/SpryMenuBarRightHover.gif", enableKeyboardNavigation: true}, );
Unfortunately this does not appear to work. According to other sources I could find (a few years old) the keyboard navigation is itself buggy; making it preferable to design one's own interface.
Tabbing the menu is successful - but will not prompt flyout sub menus - meaning that all submenu navigation through tabbing is blind (ironically that is, unless all css and javascript is stripped away, thus revealing the base html unordered list and hrefs).
Much to my surprise, keyboard interaction (via arrow keys) is enabled by default. Tabbing is only suitable for selecting non-submenu items.