Sponsoring resource downloads

Methods, systems, and apparatus, including computer programs encoded on a computer-readable storage medium, and including a method for providing content. The method comprises receiving a request from a mobile device to load a resource and determining a transmission cost for loading the resource over a metered network. The method further comprises identifying sponsored content items for delivery with the resource, the sponsored content items being included in slots for presentation along with third-party content associated with the resource, each sponsored content item having an associated bid that represents an amount that will be paid by the sponsor for presentation of a given sponsored content item. The method further comprises determining a credit to be awarded toward load costs based on the bid, and providing a label that indicates a reduced cost to load the resource when a load of a resource is partially or entirely sponsored based on the credit.