Essential steps toward establishing credibility in computational fluid dynamics (CFD) simulations are outlined, and a vision for the process of systematic collaborative validation that is open to public scrutiny via the Internet is suggested. It begins with an exposition of the elements of CFD simulations and reviews protocols useful for establishing credibility. The various sources of uncertainty in CFD, which include the skills of the user, are presented. Lessons learned from collective verification and validation exercises done in the past are surveyed and lead to our suggestion for a systematic validation process that requires the creation and use of a detailed flow taxonomy for the given application field. The code validator uses the taxonomy and an electronic database to carry out the validation process. This database archives but also gives easy access to trustworthy data and allows full public discussion and scrutiny of the information, comparisons, and hypotheses so that judgments and conclusions about the validation may be accepted or rejected by the scientific community at large. The taxonomy also is the basis on which the code user transfers credibility from previously validated generic flow cases to the simulation at hand.