In recent years, there is a growing interest in developing online collaborative learning environments. In a learner-centered online collaborative environment, students work together to construct knowledge and negotiate meanings through collaborative learning activities. Computer-mediated conference can not only greatly amplify human intellect online, but also enhance collaboration and facilitate active knowledge construction (Harasim, 1990). However, anecdotal experiences indicate that problems may arise in online learning environments without appropriate guidance and support for students. According to Vygotsky's zone of proximal development (ZPD), scaffolding is an integral part of the meaning making process in a collaborative learning environment. Therefore, a case study was conducted on an undergraduate online seminar to explore whether and how the pre-seminar designing and planning process had scaffolded the student online activities and affected online moderation. Qualitativ...