Method for automatically monitoring and verifying advertising content during a campaign, delivered over a data network. Accordingly, one or more advertisers submit, via a user interface, a list (that may be generated manually or by the mapping crawlers) of sites or of sections per site, on which the advertising content should be placed according to a desired insertion order (the insertion order information may modified at any time point). In addition, one or more mapping crawlers are activated to visit these sites and locate pages with advertisements that belong to required sections, pages that do not belong to the required sections or pages with high probability for incidents. A list of pages to visit per every site is generated and autonomous or Plug-in visual crawlers are allowed to visit the list of pages, according to a predetermined site visiting plan. A crawlers' manager allocates the pages between visual crawlers, for obtaining required adequate incident coverage and load on the visual crawlers. An incident identifier compares the insertion orders with the delivery data and whenever an insertion order and its corresponding delivery data do not match, an incident report is generated.