Advances in Web client technology now enable a richer interface thus supporting the application of visualization to the Web search process. This paper describes a user-centred evaluation of a novel visual search interface. The interface is designed to transparently support both Boolean and frequency models of information retrieval. The interface displays queries and returned results in a single simple graphical representation called Search Sphere. In contrast to both approaches that represent only queries visually and approaches that represent only results visually we integrate queries and result sets in a single visualization. We performed a user-centred study to evaluate both search query and result set comprehension. Comprehension in this context is defined as a user’s correct interpretation of a given query and also his/her ability to select relevant documents from the result set visual. The feedback of this pilot study will be used to guide the development of a second prototype consisting of a rich client visual Web search interface.