Although its conceptual origins can be traced back a few decades (Bush, 1945), it is only recently that hypermedia has become popularized, principally through its ubiquitous incarnation as the World Wide Web (WWW). In its earlier forms, the Web could only properly be regarded a primitive, constrained hypermedia implementation (Bieber & Vitali, 1997). Through the emergence in recent years of standards such as eXtensible Markup Language (XML), XLink, Document Object Model (DOM), Synchronized Multimedia Integration Language (SMIL) and WebDAV, as well as additional functionality provided by the Common Gateway Interface (CGI), Java, plug-ins and middleware applications, the Web is now moving closer to an idealized hypermedia environment. Of course, not all hypermedia systems are Web based, nor can all Web-based systems be classified as hypermedia (see Figure 1). See the terms and definitions at the end of this article for clarification of intended meanings. The focus here shall be on hypermedia systems that are delivered and used via the platform of the WWW; that is, Web-based hypermedia systems.