Mark Pilgrim and Sam Ruby have announced the launch of a RSS validator service. The service is optimized for the recently proposed RSS 2.0 format, but supports prior versions. This is some excellent work! I particularly appreciate the friendly and instructive error messages is generates. This validator will be quite helpful and instructive to those who do not understand (or simply don’t have the patience for) the mostly vague and loosely worded documentation. Being valid RSS does not guarantee that a feed’s content is well-formed enough to be useful to an end user.