Web application development differs from the development of traditional software in several significant ways; therefore requirements engineering for web applications entails new demands accordingly. This paper proposes an extreme web requirements engineering - mockup-driven fast-prototyping methodology to help elicit and finalize system requirements, as well as facilitate adjustment to quickly changing user requirements typical to web applications. Supporting the inclusion of customer feedback early in the development process, this strategy minimizes the risk of wasting valuable development efforts because of ambiguous or incomplete specifications. Real-life experiences of the use of the methodology in industry are reported as examples.