This research work falls on a multidisciplinary domain, where there is a cross feeding between Computer, Information Sciences and Cognitive Sciences. This PhD dissertation has focused on the interaction and collaboration issues in Web-based experimentation. Such context is very complex because (i) while using a Web-based experimentation environment, students can carry out their hands-on activities in a flexible way, (ii) the online learning community is heterogeneous and members have different roles, and (iii) the Web-based experimentation environment itself may integrate a large variety of software components. A framework including a set of models that capture the main features relevant to the complex context of Web-based experimentation in engineering education, the proposed solution and implementation is presented in this dissertation. These models also integrate an extension of the concept of mediation artifacts, which can be experimental results, uploaded documents, or any kind of shared instruments that can be used for supporting and facilitating the online collaborative hands-on activities. Three major aspects in interaction and collaboration that are supported by the mediation artifacts have been addressed, which are the continuity of interaction, the awareness, and the evaluation. First, the notion of continuity of interaction has emerged as an objective that could help users in obtaining a higher quality of interaction and collaboration in a complex environment. The continuity of interaction emphasizes the uninterrupted sequence of activities. I presented the sources of the discontinuity or interaction in such online learning community. I also presented an analysis grid including several dimensions of continuity of interaction. In fact, the artifacts can be exploited to support the interaction between heterogeneous software components constituting the environment; and this process help facilitate the collaboration among users. The provided mechanism is called artifact-based continuity of interaction. Second, I discussed various crucial features of awareness in Web-based experimentation. The artifacts can actually be collected in a public workspace and shared among users. Then the artifacts stored in the workspace can be retrieved, analyzed, and visualized to provide so-called artifact-based awareness that supplies information not only about others' interaction and learning activities but also about the social structure of the whole online learning community. Third, I discussed various evaluation issues related to Web-based experimentation environments. I proposed a model for the evaluation of Web-based experimentation environments, namely the Instrumentation Feedback Model for Evaluation. I also proposed a set of general and artifact-based metrics for measuring various aspects relevant to an online learning community in a Web-based experimentation environment. I also present an extended Web-based laboratory journal for students in engineering curricula, namely eJournal, which is an implementation of the concept of mediation artifacts. The eJournal has been deployed and utilized in many engineering courses at the Ecole Polytechnique Fédérale de Lausanne (EPFL) and other European institutions. Lastly, the dissertation presents an evaluation process carried out from the 2002 winter to the 2005 summer semesters in the automatic control laboratory courses offered by the School of Engineering at the EPFL. The objectives of the evaluation are to study and validate the proposed approach in sustaining interaction and collaboration in the context of Web-based experimentation as well as to improve the utility and usability of the provided environment.