Current web site development is still dominated by technical issues. In order to enable efficient communication between developers and to provide a stable foundation for adopting new technologies, conceptual modeling of web sites is essential. Based on the state-of-the-art of conceptual modeling as implemented in current CASE environments, this paper tries to identify the “essence” of a web site and proposes an adequate conceptual model. The model is intended to capture not only hierarchical document structure and hypertext semantics, but also dynamic page generation from databases and various approaches to explicit and implicit navigation. It becomes evident that web sites can be regarded as supersets of traditional information systems, thereby requiring conceptual modeling to include various additional features. The proposed model comprises several classes of information objects, various types of associations, design rules, and quality checks. For illustration purposes, the model is applied to an existing web site. Current web site development tools are analyzed with regard to the extent to which conceptual web site modeling is supported.