The importance of commercial Web sites has been grown as their performance is coming out. As the widespread use and dependency on Web technology increases, so does the need to assess success factors of Web sites. Yet, there are not rigorous methods to evaluate Web sites. Some metrics for Web sites have been proposed, but they are primarily anecdotal and exploratory. This thesis proposes Web site success factors, such as system quality, information quality, service quality, and entertainment quality, which can be useful for evaluating Web sites. The research framework is derived from the theories of information systems and marketing. It analyzes 474 Internet users and verifies hypotheses. A comparative study of Web site types, such as finance, e-commerce (shopping mall), and entertainment domain is performed. We confirm positive relationships among proposed Web site success factors and Web site success index such as satisfaction and loyalty. In addition, we also confirm differences among Web site types in users’ recognition and influences of those success factors.