A method and a system are provided for blending advertiser data with ad network data in order to serve finely targeted ads. In one example, the system receives campaign information from one or more advertisers. The campaign information includes at least one of a budget, criteria, and a creative. The system receives a notification from a user device about an available ad spot on a webpage for display at a browser running on the user device. The system receives data from an advertiser. The data from the advertiser pertains to managing an ad to be sent to the user device to fill the ad spot on the webpage. Then, the system combines the data from the advertiser with data from an ad network to obtain combined data. The ad network is configured for managing at least part of an ad campaign. The advertiser is also configured for managing at least part of the ad campaign.