Two methods are currently used to organize and retrieve information on the Internet. Search engines like Google and AltaVista use a robot-based keyword searching method by constructing inverted index files for Web pages and matching users’ query terms with the index terms. The other method organizes human-selected Internet resources into a searchable database, and gives users structured hierarchical access to the database in a similar way to browsing through library classification schemes. We call this structured hierarchical system a Web directory. Knowledge structures, like a library classification schema or a Web directory, visualize and reflect what people know about things, and help people understand things better, identify gaps, recognize patterns, predict future trends, and so forth (Kwasnik, 2005). Moreover, Web directories offer quality control and give access only to selected Internet resources. All these advantages make the browsing structure based on subject classification a desirable complement to the search engine type service (Koch, Day, Brümmer, Hiom, Peereboom, Poulter, & Worsfold, 1997).