This paper presents the development and evaluation of a World Wide Web-based lesson developed to cultivate situated learning. This research employed the quasi-experimental method along with semi-structured interviews to investigate the effects of a Web-based lesson on science learning in the senior high school level. Three classes of second-year students from two senior high schools in Taipei (Taiwan) were selected as the participants for the study. A total of 110 students participated, including 49 males and 61 females. The statistical results indicated that: (1) students' conceptual progress almost reached a significant level before and after the experiment; (2) there were significant differences between male and female students on their conceptual progress before and after the experiment; and (3) most students had positive opinions about the Web-based lesson. Analysis of qualitative data indicated that some students thought that the Web-based lesson, named Lesson Rainbow, provided a daily-life situation that could promote their motivation for learning and help them integrate knowledge. (Contains 22 references.) (Author/MES)