1. A method of targeting a content item performed by a data processing apparatus, the method comprising: receiving placement criteria associated with a campaign, the placement criteria specifying at least one web property to which advertisements associated with the campaign are targeted independent of page keywords that are associated with the at least one web property; receiving target keywords associated with the campaign, each target keyword specifying at least one term that must be matched by a page keyword for the at least one web property for advertisements associated with the campaign to be provided for presentation with the at least one web property; receiving a content item request for a content item, the request including data defining a requesting web property for which a content item is to be provided; identifying the placement criteria satisfied by the requesting web property, the identification being independent of page keywords that are associated with the requesting web property; identifying one or more target keywords that are matched by one or more page keywords that are associated with the requesting web property; selecting a content item to be provided with the requesting web property, the selected content item being associated with: the campaign; at least one target keywords that is matched by at least one of the one or more page keywords for the requesting web property; and at least one placement criteria satisfied by the requesting web property, the placement criteria being satisfied independent of the one or more page keywords that are associated with the requesting web property; and providing the selected content item for presentation with the requesting web property.
5. The method of claim 1 , wherein the selected content item is an advertisement that is associated with the campaign, the at least one target keyword, and the at least one placement criteria.