In this paper, we propose a method for mediatory summarization, which is a novel technique for facilitating users' assessments of the credibility of information on the Web. A mediatory summary is generated by extracting a passage from Web documents; this summary is generated on the basis of its relevance to a given query, fairness, and density of keywords, which are features of the summaries constructed to determine the credibility of information on the Web. We demonstrate the effectiveness of the generated mediatory summary in comparison with the summaries of Web documents produced by Web search engines.