15. One or more computer-readable non-transitory storage media embodying software that is operable when executed to: by a code segment executing on a client computing device and embedded in a first structured document rendered by the client computing device, detect an event on the first structured document, the event directing the client application to generate a first request for a second structured document from a remote server; by the code segment, intercept the first request; by the code segment, identify one or more resources specified in the first request that are not currently stored on the client computing device; by the code segment, generate a second request for resources to be sent to the remote server, wherein the second request specifies only one or more of the resources specified in the first request that are not currently stored on the client computing device; send the second request to the remote server; receive, in response to the second request, one or more of the resources specified in the second request; and render the second structured document with: one or more of the resources specified in the first request that are currently stored on the client computing device; and one or more of the resources received in response to the second request.
15. One or more computer-readable non-transitory storage media embodying software that is operable when executed to: by a code segment executing on a client computing device and embedded in a first structured document rendered by the client computing device, detect an event on the first structured document, the event directing the client application to generate a first request for a second structured document from a remote server; by the code segment, intercept the first request; by the code segment, identify one or more resources specified in the first request that are not currently stored on the client computing device; by the code segment, generate a second request for resources to be sent to the remote server, wherein the second request specifies only one or more of the resources specified in the first request that are not currently stored on the client computing device; send the second request to the remote server; receive, in response to the second request, one or more of the resources specified in the second request; and render the second structured document with: one or more of the resources specified in the first request that are currently stored on the client computing device; and one or more of the resources received in response to the second request. 20. The media of claim 15 , wherein one or more of the resources specified in the first request that are currently stored on the client computing device comprise cached content shared between the first and second structured documents.