collapsible hierarchical menu navigation javascript (accessible)

I've created a JavaScript navigation system and would appreciate any
feedback anyone might have about it and the techniques I've used to make
it accessible. A sample of it in action is at
http://courses.iddl.vt.edu/samplecourse/.  The JavaScript is at
http://courses.iddl.vt.edu/samplecourse/navigation.js.

 

I had trouble finding collapsible hierarchical menu navigation scripts
that degraded well when JavaScript was not present.  They all used
JavaScript to create the menu, which wasn't entirely kosher from an
accessibility perspective.  I wrote a script that works with the list
markup that is in a page already and thus users can access the
navigation even if JavaScript is turned off.  It doesn't have some of
the bells and whistles of the other scripts I've seen (though it has
some unique coolness such as automatic breadcrumbing and prev/next
links) but it is small, simple, DOM-based, and, I believe, accessible.
I've tried it out on WinXP with Netscape 4.7 and 6.0 and higher, Mozilla
1.0, Opera 6.02, Phoenix 0.1, Mac OS X with Safari 1.2.2, IE 5.2,
Mozilla 1.5, Firebird 0.7, and Opera 6.03, Mac OS 9.2.2 with IE 5.0,
Opera 5.0, Netscape 4.77 and 6.0, and the latest version of JAWS on
WinXP.  The important functionality is available in all those listed
(keyboard access to all the links in the list markup) and the other
functionality is available in most of those listed.  The only real duds
are older versions of Opera and Netscape 4.7, though as I said, even
those allow access to the links.

 

Rob