A method of providing targeted online advertisement includes receiving a request for an ad impression. The request includes a first content and a second content. The method also includes determining information related to (i) a context of the first content, (ii) a context of the second content, and (iii) a correlation between the context of the first content and the context of the second content, and providing the determined information to a bidding service, thereby enabling one or more advertisers to place one or more bids on the ad impression based on the provided information. Each of the one or more bids includes a bid price. The method further includes receiving the one or more bids for the ad impression, selecting one of the one or more received bids based at least in part on the bid prices, and providing an ad impression associated with the selected bid.