Formal methods have already been shown to improve the development process and quality assurance in system design and implementation. This is an examination of whether these benefits also apply to the field of human-computer interface design and implementation, and whether formal methods can offer useful support in usability evaluation and obtaining more reliable implementations of user requirements. The main aim of this text is to compare the different approaches and examine which particular type of implementation and problem each one is best suited to. To enable the reader to compare and contrast the approaches as easily as possible, each one is applied to the same case study - the specification of an ideal Netscape-like Web browser and HTML page server.