Online learning of click-through rates on search result blocks from one or more federated sources may be provided. Click-through feedback for the search result blocks may be received from the one or more federated sources in response to a query. Weights may be assigned to each of the search result blocks based on the received click-through feedback. The search result blocks may then be ranked based on the assigned weights. Finally, a search results page may be generated for displaying the ranked search results blocks to a user.