Trying out the quiz I submitted my perfect answers to be greeted by:
"The requested file was not found"
PvR

Eric Haines schreef
Hmmm, you're right! I've moved it (and my wildflower and bird
identification programs) to:

http://www.realtimerendering.com/trees/trees.html

and the quiz to

http://www.realtimerendering.com/trees/treequiz.html

This should be a more stable site anyway. Sorry about that!

Eric