This research investigates university students' determinations of credibility of information on Web sites, confidence in their determinations, and perceptions of Web site authors' vested interests. In Study 1, university-level computer science and education students selected Web sites determined to be credible and Web sites that exemplified misrepresentations. Categorization of Web site credibility determinations indicated that the most frequently provided reasons associated with high credibility included information focus or relevance, educational focus, and name recognition. Reasons for knowing a Web site's content is wrong included lack of corroboration with other information, information focus and bias. Vested interests associated with commercial Web sites were regarded with distrust and vested interests of educational Web sites were not. In Study 2, credibility determinations of university students enrolled in computer science courses were examined for 3 provided Web sites dealing with the same computer science topic. Reasons for determining Web site inaccuracy included own expertise, information corroboration, information design and bias. As in Study 1, commercial vested interests were negatively regarded in contrast to educational interests. Instructional implications and suggestions for further research are discussed.