liam quinn appears to agree that the formal public identifier is the only case sensitive part of the doctype. in his validator's faq example[1] he writes:
<!doctype html public "-//W3C//DTD HTML 4.0 Transitional//EN">
as valid.
- p
1. http://www.htmlhelp.com/tools/validator/problems.html.en#doctype-case
-- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]