1. A centralized system for selecting, from a plurality of advertisements, at least one advertisement for presentation to a user, comprising: one or more server-readable criteria repositories comprising at least one criterion associated with at least one advertisement; one or more servers operable to: receive an advertisement request; interface with one or more server-readable data repositories; retrieve from the one or more server-readable data repositories information required to evaluate one or more of the criterion; evaluate one or more of the criterion to determine advertisements the user is eligible to receive; rank a plurality of eligible advertisements by, at least in part, bids associated with the eligible advertisements, wherein at least one of the bids is a static value and at least one of the bids is a value computed by the system.