Building large-scale web sites is difficult. To make matters worse, keeping them up-to-date, consistent and error-free is even harder. A good way to alleviate these problems is to have the web site be created automatically, and to do so by precisely defining what the web site should consist of and to state how to continually derive the final web site from it's definition. The definition of a web site's content, structure, design, and behaviour is ideally given by a formal specification. This book shows how to successfully employ formal specifications to describe and generate web sites. An interesting new way for achieving this is using functional languages to write down the specifications, making them powerful, concise, high-level, and maintainable. A description of a coherent approach is delivered, underpinned by examples that demonstrate its applicability, and providing new insights into the possibilities that lie in functional web site specification.