1. An online content evaluation system comprising: a scanning server to scan web sites and to collect metrics for online ads the metrics including coverage, targeting, and delivery metrics, wherein each web site has a hierarchy of web pages starting at a home page, wherein to collect the metrics, the scanning server determines a location of the online ads in the hierarchy of web pages and a location of the online ads in the web pages, and wherein the scanning comprises: parsing web pages for the web sites, identifying computer code from the parsed web pages, wherein the computer code is a regular image expression or a click thru URL, determining whether the computer code includes information identifying the online ads as online ads for a predetermined company, and determining values for the metrics for the online ads identified as online ads for the predetermined company; data storage storing the values for the metrics for the online ads; and a content evaluation server to classify online ads, wherein to classify the online ads, the content evaluation server: classifies the online ads into candidate groups based on the metrics and metric values, wherein, for each candidate group, the online ads classified into the candidate group are estimated to be in a same ad campaign; executes a group merging process to merge at least some of the candidate groups, wherein to execute the group merging process, the content evaluation server: selects candidate groups for comparison based on a determination that time periods for online ads in the candidate groups overlap, and on indications that the candidate groups are associated with a same campaign; merges the at least some selected candidate groups based on the metrics, including visual and non-visual metrics for the online ads in the at least some selected candidate groups, wherein the visual metrics include text, color, and size, of each of the online ads and the non-visual metrics include domain name and filename of each of the online ads; and determines campaign groups at least from the merged groups; and assigns an ad campaign to each campaign group.