The World Wide Web (WWW) is a successful hypermedia information space used by millions of people, yet it suffers from many deficiencies and problems in support for navigation around its vast information space. In this paper we identify the origins of these navigation problems, namely WWW browser design, WWW page design, and WWW page description languages. Regardless of their origins, these problems are eventually represented to the user at the browser’s user interface. To help overcome these problems, many tools are being developed which allow users to visualise WWW subspaces. We identify five key issues in the design and functionality of these visualisation systems: characteristics of the visual representation, the scope of the subspace representation, the mechanisms for generating the visualisation, the degree of browser independence, and the navigation support facilities. We provide a critical review of the diverse range of WWW visualisation tools with respect to these issues....