End-users tend to lose their way in the maze of information within hypertext. Much work done to address the "lost in hyperspace" problem is reactive, that is, doing remedial work to correct the deficiencies within hypertexts because they are (or were) poorly designed and built. What if solutions are sought to avoid the problem? What if we do things well from the start? This thesis reviews the "lost in hyperspace" problem, and suggests a framework to understand the design and usability issues. These issues cannot be seen as purely psychological or purely computing, they are multi-disciplinary. The proactive, multi-disciplinary approach undertaken in this thesis is drawn from current technologies in sub-disciplines of hypertext, human-computer interaction, cognitive psychology and software engineering, and they include investigations into: " good design principles and guidelines for the building of hypertexts in the first place; " task analysis and user modelling techniques for end-users' tasks to be carefully defined; " effective hypertext structures to ensure usability of hypertexts; and " designer tools to create hypertexts with a reduced tendency for the "lost in hyperspace" problem to arise. To demonstrate these ideas, this thesis presents HyperAT, a hypertext research authoring tool, developed to help designers build usable web documents on the World Wide Web. The World Wide Web is chosen as a hypertext example since it is the most widely used and largest hypertext system ever. The approach taken in HyperAT is novel: multi-disciplinary approaches are integrated and implemented with a practical authoring tool. Evaluation of HyperAT indicates that it does address the "lost in hyperspace" problem, particularly for the World Wide Web by: (i) helping designers manage the complexity of the design and validation processes; and (ii) helping hypertext end-users navigate hypertexts produced by HyperAT without getting "lost".