The World Wide Web has had over 5 years of intensive development, and has expanded from a text-only technical documentation system to a multimedia information base distributed across the planet. Although its tool for structural definition, the Hypertext Markup Language (HTML), has been under constant development throughout this period, most browsers have been slow to take advantage of all the facilities it offers. At a time when there is much debate over the public future of the Web, it is in danger of partial stagnation. Despite significant innovations in some areas, the field is still open for software developers who are capable of harvesting the benefits of SGML, the language in which HTML is written. This analysis of HTML Document Type Descriptions (DTDs) reveals where some of the opportunities may lie.