1. A method for ranking one or more advertisements, the method comprising: retrieving a result set comprising one or more advertisements responsive to a request; for the one or more advertisements comprising the result set, calculating a clickability score; for the one or more advertisements, calculating an expected revenue for a given advertisement using the clickability score for the given advertisement and an indication of revenue associated with the given advertisement; and ordering the one or more advertisements according to the expected revenue of the one or more advertisements.