The development of computer technology and telecommunications network technology has brought about a paradigm shift in communication between firms and customers. In particular, computer-mediated communication in the Internet environment has had a significant impact on firms' marketing and advertising efforts. Amid these changes, corporate Internet sites that include product advertising—namely, homepage advertising—have gained prominence, yet specific empirical research on their execution strategies has been insufficient. Based on prior studies, this research investigates how three core attributes provided by Internet sites—(1) informativeness as a utilitarian benefit, (2) entertainment as a hedonic benefit, and (3) interactivity as a medium characteristic of computers in the Internet environment—affect product advertising on Internet homepages through the mediation of Internet site attitude. The empirical analysis results are as follows. First, when the attribute beliefs of Internet sites—informativeness (H1), entertainment (H2), and interactivity (H4)—were perceived as higher by users, attitudes toward the Internet site were more favorable. At this point, informativeness and entertainment had mutual influence on each other (H3), and interactivity enhanced Internet site attitude by increasing the perceived levels of informativeness and entertainment (H5). Second, a strong causal relationship was found between Internet site attitude and Internet advertising attitude (H6), indicating that the attribute beliefs of Internet sites influence Internet advertising attitude through the mediation of Internet site attitude.