This study examines how one student pair working face-to-face at a computer and engaged in a web-based discussion environment negotiated meanings for their activity and what contextual resources they used in this negotiation process. The aim was also to study how the students themselves interpreted the learning activity. The subjects were two secondary school students (aged 15) participating in a web-based history project. Data was collected by various means in order to validate the findings. Linell's [(1998). "Approaching dialogue. Talk, interaction and contexts in dialogical perspectives." Amsterdam: John Benjamins Publishing Co.] notion of contextual resources was used as an analytical tool in studying how students constructed knowledge and negotiated meanings in their activity. Because contextual resources comprise not only the concrete resources (e.g. books) but also more abstract and mediated resources (e.g. socio-cultural contexts), the students' discursive activity was analysed to identify common features or patterns of interaction from the data. Results showed that students' meaning negotiations was framed and mediated by students' comprehension of (school) knowledge, which directed the way resources were used in the situation and which resources were considered legitimate to use in the school context. In addition, students' habitual use of communication technology, which came outside the formal school activities, made up a situational frame and was manifested in the hectic communicative approach adopted in the situation. Altogether, the study demonstrated the situated and mediated nature of learning activity.