1. A computer-implemented method for validating on-line advertising sales, comprising the steps of using a computer system for: (a) receiving an on-line order for placement of on-line advertising from a prospective advertiser submitted via the Internet to a web site that sells advertising; (b) obtaining at least one of a Uniform Resource Locator (URL) and domain name to be advertised; (c) performing processing on at least one of the URL and domain name to associate a physical business address or business entity with said URL or domain name, comprising: checking a domain name or domain included as part of said URL against a database of known domains for which integrity ratings are available to eliminate unnecessary reprocessing of domains already evaluated; if the domain is in the database indicating an integrity rating is already available, bypassing further processing and returning an integrity rating immediately; if the domain is not already in the database, using name and address extraction to attempt to obtain an entity name and physical address associated with the URL or domain name; if a reliable entity name and physical address are obtained, collecting business information; scoring the business information; and using the scored business information to at least one of compute the integrity rating and to update the integrity ratings in the database of known domains so that future similar queries can be quickly processed; (d) determining an integrity rating for said URL or domain name; (e) testing the integrity rating against a threshold of acceptability; and (f) if the integrity rating is below the threshold of acceptability, rejecting the placement of the on-line advertising; thereby preventing advertisers of questionable legitimacy from placing advertisements on web sites, improving customer satisfaction, increasing the value of the advertising medium, and making the advertising space more valuable.