Among other disclosure, a method includes receiving first electronic content configured for displaying a first page in a browser, the first electronic content including a document object model for the first page. Content in the document object model is identified as corresponding to at least one advertisement on the first page, the first page further including page content. Information is extracted from the identified content to be used in identifying an advertising network system that the advertisement links to. An identity of the advertising network system is determined using the extracted information. Second electronic content is generated using the first electronic content and the determined identity of the advertising network system. A second page including the page content of the first page and the advertisement is generated and displayed. On the second page the advertisement is labeled with the determined identity of the advertising network system.