Although not all search tools permit the use of the Boolean operators AND, OR, and NOT, most do use relevancy ranking for retrieval and display. The documentation accompanying many of the prominent search tools is replete with claims about speed, database size, search features, accuracy, and precision. The truth is, even the smaller search tools will sometimes retrieve useful material that the bigger ones miss. There is also no unanimous agreement on how to best calculate the size of a search tool's database.
Some tools only count the Web pages they have actually retrieved and indexed.
Others also include the number of links mentioned in those retrieved pages. Try several to ensure a more complete search. Almost all the search tools listed below provide helpful search tips. You may also wish to examine the Search Engine Watch site for more valuable information and resources on search engines. There is also a guide to Getting the most out of Guides and Search Engines that may prove useful in your work or research.