1. A method for verifying relevance between terms and Web site contents, the method comprising: retrieving site contents from a bid URL; formulating expanded term(s) semantically and/or contextually related to bid term(s), generating content similarity and expanded similarity measurements from respective combinations of the bid term(s), the site contents, and the expanded terms, the similarity measurements indicating relatedness between respective ones of the bid term(s), site contents, and/or expanded terms; calculating category similarity measurements between the expanded terms and the site contents in view of a similarity classifier, the similarity classifier having been trained from mined web site content associated with directory data; calculating a confidence value from combined ones of multiple similarity measurements, the combined ones comprising content, expanded, and category similarity measurements, the confidence value providing an objective measure of relevance between the bid term(s) and the site contents.