Methods, systems, and apparatus include computer programs encoded on a computer-readable storage medium for conducting a selection process for load order. A method includes: identifying a plurality of winners of a first selection process for displaying content in a block including identifying first and second winning content items and an associated placement of the first and second content items in the block; determining when the first content item or second content item has a bid specified for a load order for the block; when both the first and the second content item have a bid specified for load order, conducting a selection for load order based on the respective bids; determining a winner of the selection and enabling the winner to load first when the block is rendered on a user device; and charging the winner based at least in part on the bids.