1. One or more computer-readable storage media excluding signals per se having embodied thereon computer-executable instructions that, when executed, perform a method comprising: providing a set of search results returned in response to a search query composed and issued by a user; determining a ranking of the set of returned search results against each other as a function of relevance to the issued search query; selecting for evaluation one or more search results from the returned set of search results based on the ranking; determining a level of quality, that is independent of the terms of the search query, for each of the one or more selected search results from the returned set of search results by employing a classification process, wherein the classification process comprises: targeting features demonstrated by the one or more selected search results to be evaluated; evaluating the targeted features to generate a level-of-quality score for each of the one or more selected search results, wherein the level-of-quality score is evaluated using a cross-result entropy that quantifies a level of similarity between a plurality of the search results, and wherein the search engine is configured to decrease the level-of-quality score based on determining that the cross-result entropy is sufficiently high; comparing the level-of-quality score against a predefined threshold value; and based on the comparison, assigning each of the one or more selected search results an absolute measurement, wherein the absolute measurement indicates good quality when the level-of-quality score is greater than the threshold value, and wherein the absolute measurement indicates poor quality when the level-of-quality score is less than the threshold value; calculating a level of confidence that a rewritten search query will provide new search results that improve the set of search results; automatically rewriting the search query by the search engine to generate the rewritten search query, wherein each key word of the rewritten search query is automatically selected for inclusion in the rewritten search query; and based on the calculated level of confidence indicating that the rewritten search query will provide the new search results that improve the set of search results, and based on identifying that the absolute measurement assigned to at least one of the one or more selected search results indicates the poor quality, automatically conducting a search with the rewritten search query.