This paper presents the development and evaluation of a web-based lesson--Lesson Rainbow. This lesson features multiple representations (MRs), which purposefully deliver concepts in relation to distinctive disciplinary subject areas through story-based animations that are closely related to learners' life experiences. The researchers selected 58 2nd-year junior high school students as the participants (32 males and 26 females). A quasi-experimental method together with semi-structured interviews was utilized. This research project was intended to investigate students' conceptual progress, and to evaluate the use of MRs and of situated learning components in the design of Lesson Rainbow. The statistical results indicated that: (1) students' science concepts significantly increased ("t" = 3.84, "p" less than 0.01) through the use of Lesson Rainbow, and (2) students thought that the use of MRs in this web-based lesson was an effective pedagogical tool in as much as it allows for the learning of specific theoretical viewpoints in addition to the necessary background information. Lesson Rainbow employing MRs helps learners to understand the meanings of, and interrelationships between, different kinds of external representations. This kind of design facilitates their understanding of the correspondence between abstract symbolic expressions and real-world situations.