Introduction 1.1 The problem The World-Wide Web (WWW) (CERN, 1994) is a network-based standard for hypermedia documents that combines documents prepared in HyperText Markup Language (HTML) (NCSA, 1994a) with an extensible set of multimedia resources. The most popular WWW browser with available source code is Mosaic (NCSA, 1994b), a cross-platform program developed and distributed by NCSA, now running in X11-based Unix, Macintosh and PC-Windows environments. As a hypermedia viewer, Mosaic combines the flexibility and navigability of hypermedia with multimedia outputs such as audio and GIF images. The World-Wide Web, especially as viewed with Mosaic, is phenomenally popular. By mid-Spring of 1994, Internet traffic was doubling about every six months. Of this growth, 2 the World-Wide Web's proportional usage was doubling approximately every four months. In absolute volume of traffic, use of the WWW was doubling every two and a half months (Wallach, 1994). Much of the popu