The growing demand for web applications and the new multi-user and multi-device requirements of these has led to the need for a structured and well-reasoned approach that helps both the application designer and the developer to produce a good quality product. On one hand we have the application designer, who has to describe all aspects of the application and manage the complexity of the tasks; on the other hand both the application customer and the developer need to validate and understand the designer's choices. To conciliate these needs, we propose a prototyping framework based on W2000 [1][2] methodology: in this way the designer has a powerful tool to keep control over the web application, the customer has a point of reference for evaluating the design, and the developer can better understand the design thanks to the prototyped application.