Much is unknown about the effectiveness of networked technology in education. Although a great deal of research exists dealing with the effectiveness of various types of web-based learning systems, the focal question of most evaluation studies does not concern the innovation of the delivery model itself and the factors that contribute to its effectiveness. Moreover, there is a lack of a theoretical or conceptual framework in many existing studies. The authors applied a systematic evaluation method (called CADMOS-E), and present the quantitative and qualitative results of a re-evaluation study on the effectiveness of a web-based learning system used at the National Technical University of Athens (NTUA), Greece, over a period of three years (1998, 1999, and 2000). The system supports an introductory course in software engineering offered by the Software Engineering Laboratory of the Electrical and Computer Engineering Department at the NTUA. The findings were compared with the results from a study done in 1997. According to that study the "quality of the learning material" alone explained almost 28% of the system's effectiveness (R2adj.= 0.278). After its first evaluation the system underwent a number of revisions and additions suggested by the results from quantitative and qualitative analysis of students' feedback. In this article, among other things, the authors demonstrate--using quantitative results--that the changes made in the design and presentation of the learning material resources improved the learning effectiveness of the revised system, from 28% to 37.5%. (Contains 3 tables.)