ok, my file now validates to html 4.01 (circa 1998)
and to html 3.2 (circa 1996), so i'm satisfied i have
enough backwards compatibility. ;+)
of course, it also runs in the browser you're running
today, and the one you'll run next year, and the year
after that. and it's got all the e-book functionality
that one can reasonably expect from a web-browser.
thanks for all your help! :+)
-bowerbird