10. A method of searching documents containing one or more search terms entered in a search window and displaying search results of the search, the method comprising: searching a plurality of documents by using a computer to define a plurality of search results classes based on characteristics of the documents in search results, wherein the searching is based on the one or more search terms entered by a user; determining a perceived relevance for the search results classes based on a number of times search identifier terms associated with the search results classes appear in documents that are returned from prior searches included the one or more search terms, and wherein the determining further based on an aggregate document similarity score for the documents identified by the search, such that the perceived relevance of the search results classes is determined at least in part by actions of prior users performing searches including the same one or more search terms, and at least in part by the number of times the search identifier terms appear in the documents identified by the search; displaying a plurality of selectable search results classification tabs on a display device, the search results classification tabs corresponding to search results classes, and the plurality of search results classification tabs displayed in a changeable order determined by the perceived relevance of the corresponding results classes such that a first search results classification tab corresponding to a search results class having a higher perceived relevance is displayed ahead of a second search classification tab corresponding to a search results class having a lower perceived relevance; displaying search results associated with a search results class in a search result display window on the display device when a search results classification tab of the search results classification tabs corresponding to a search results class of the search results classes has been selected; and refining the search results upon selection of a search term clarification button either before or after one or more search terms are entered into the search window.
10. A method of searching documents containing one or more search terms entered in a search window and displaying search results of the search, the method comprising: searching a plurality of documents by using a computer to define a plurality of search results classes based on characteristics of the documents in search results, wherein the searching is based on the one or more search terms entered by a user; determining a perceived relevance for the search results classes based on a number of times search identifier terms associated with the search results classes appear in documents that are returned from prior searches included the one or more search terms, and wherein the determining further based on an aggregate document similarity score for the documents identified by the search, such that the perceived relevance of the search results classes is determined at least in part by actions of prior users performing searches including the same one or more search terms, and at least in part by the number of times the search identifier terms appear in the documents identified by the search; displaying a plurality of selectable search results classification tabs on a display device, the search results classification tabs corresponding to search results classes, and the plurality of search results classification tabs displayed in a changeable order determined by the perceived relevance of the corresponding results classes such that a first search results classification tab corresponding to a search results class having a higher perceived relevance is displayed ahead of a second search classification tab corresponding to a search results class having a lower perceived relevance; displaying search results associated with a search results class in a search result display window on the display device when a search results classification tab of the search results classification tabs corresponding to a search results class of the search results classes has been selected; and refining the search results upon selection of a search term clarification button either before or after one or more search terms are entered into the search window. 15. The method of claim 10 wherein selected search results class is selected either by a user or by default based on the largest perceived relevance of corresponding results classes.