Abstract. WebML (Web Modelling Language) is a language for the design of dataintensive Web sites. It is supported by visual tools allowing the definition of the conceptual data organization and of the pages and links of the actual hypertext(s) which constitute a Web application. In this paper we describe a semantic model for WebML hypertexts by means of Statecharts. Statecharts provide a formal description of the clicking behavior and page data fill of WebML applications. The proposed semantic model has guided the implementation of the WebML runtime and the construction of advanced specification checking functions embedded in the WebML design tools. In particular, developers are supported in the identification of design and runtime problems caused by non-determinism, racing conditions and deadlocks.