In this study, we propose an exploratory approach aiming at a typology of user behaviour during a Web search session. We describe a typology based on generic IR variables (e.g. number of queries), but also on the study of topic (propositions with distinct semantic content defined from the search statement). To this end, we gathered experimental data enabling us to study variations across users (N=70) for the same task. We performed a multidimensional analysis and propose a 5 classes typology based on the individual behaviours during the processing of a complex search task.