Thank you. Figured it was something simple. And, you are right, I should have re-validated the code I pulled from the tutorial. I didn't. And justly deserve stricture.
However, replacing "language" with "type", while it did render the w3c html validator to declare "This document was successfully checked as XHTML 1.0 Strict!", did not resolve my problem: firefox still does not fire the alert on closing the window.
(Verified through ctrl-u that the code was the most recent.)
At this point, I don't need the aggravation, so will live without it.
Thank you all for taking a look at it.