In one embodiment, a method includes sending, by a client device, a request to a computer server system for a target structured document. In a first response phase, a first response portion from the computer server system is sent in response to the request. The first response portion includes a first resource associated with the target structured document, wherein a likelihood that the first resource will be included in a response to a future request for the target structured document exceeds a first predetermined threshold. Further in a second response phase, a second response portion from the computer server system is sent in response to the request. The second response portion includes a second resource associated with the target structured document, wherein a likelihood that the second resource will be included in a response to a future request for the target structured document exceeds a second predetermined threshold.