A usability study was carried out to verify that a moderately complex interaction task could be supported adequately by a straightforward Web interface. The application chosen for study was NEST, an examination authoring tool mounted on the Web. The interface for NEST is of non-trivial complexity and provides a relevant case study.We report on heuristic evaluations of the system, which validated many of our design decisions. In particular, we find that a user's expectation for interface performance and layout must be balanced against the client footprint size and the volume of the interaction with the server.