12. The system of claim 8 , wherein the one or more computers are further configured to perform operations comprising determining a category to which the requesting property has been assigned, the category being determined independent of the page keywords for the requesting web property.
12. The system of claim 8 , wherein the one or more computers are further configured to perform operations comprising determining a category to which the requesting property has been assigned, the category being determined independent of the page keywords for the requesting web property. 13. The system of claim 12 , wherein the one or more computers are further configured to perform operations comprising identifying advertisements for which presentation of the advertisements is conditioned on the requesting web property being assigned to the category.