If you've used any sort of basic on-line help system, you're already familiar with the primary concept behind that of the World Wide Web: that of hypertext. On-line help systems or help stacks such as those provided by Microsoft Windows Help, Sun Microsystems' AnswerBook or HyperCard on the Macintosh use hypertext to present information. To get more information on a topic, just click on that topic. A new screen appears with that new information. Figure 1 shows a simple example of how a hypertext system works.