In an embodiment, a digital data specification of a compound advertisement comprising a plurality of ad units is received at an advertisement delivery server computer, where the digital data specification of the compound advertisement specifies one or more sequential dependencies between one or more ad units of the plurality of ad units and a bid value for each ad unit of the plurality of ad units. Based at least in part on a particular sequential dependency of the first ad unit upon a second ad unit of the same compound advertisement and a bid value associated with the first ad unit, a first ad unit of the compound advertisement is selected for display at a separate user computing device using the advertisement delivery server computer. The first ad unit is caused to display at the particular user computing device.