• The fastest way to find something on the Web is by knowing where to look. The best tips often come from colleagues and friends who work in the same area, have the same interests, or otherwise simply understand the context of your investigation. Unfortunately, the tipsters may not be around when you need them the most.
• Portals are the Web facade of an old idea: they define a context and gather information that is relevant to it. If you are interested in a specific topic, you go to a portal that covers it, just as you buy a journal that addresses the topic.
• A search engine indexes the Web and uses the index to answer a knowledge seeker's keyword queries. In principle, there are two ways to create an index: automatically by using information-retrieval techniques to scan text or manually by having an editor read it. Both approaches have their limitations. The state of the art in automated text understanding limits the accuracy of automated approaches; they also have problems in determining relevancy. The manual approach, on the other hand, is costly and difficult to pace with the evolution of the Web. So far, no search engine is able to index the whole Web.