The use of maps on the World Wide Web is revolutionising how people access information. These web maps harness text, audio, video, animation, graphics and, most importantly, user interaction to improve the communication and interpretation of geographic phenomena. In this interactive and dynamic environment, web application developers have the opportunity to allow map readers to also be map producers; users can be enabled to query and analyse data and then assemble maps and other visualisations themselves, enhancing their understanding of the data and its geospatial relationships. This thesis focuses on what factors are important for the design of web mapping applications that provide visualisations of demographic diversity. Demographic information is inherently geospatial, making maps the ideal tool for visualising population statistics and their spatial relationships. An outcome of this research is a set of guidelines for reviewing web mapping applications that portray demographic diversity information. This thesis also provides an insight into the current standard for web mapping of demographic information and identifies the potential for improvement. A review of the literature, as well as a reflexive implementation, are the principal methods used to develop these guidelines. The essential components include the needs of demographers, and principles of cartography and human-computer interaction, as well as a consideration of open source and proprietary software. Five prominent, national demographic web mapping applications (two Australian, and one from New Zealand, the United States of America, and Canada) are used to develop these guidelines, as well as providing an insight into the current standard. The main conclusion of this research is that the guidelines developed provide a worthwhile structure but need to be kept broad. Also, there needs to be more emphasis on user data upload facilities, which is important for demographers, and cartographic communication needs to be given higher priority.