1. A method comprising: by a code segment executing on a client computing device and embedded in a first structured document rendered by the client computing device, detecting 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, intercepting the first request; by the code segment, identifying one or more resources specified in the first request that are not currently stored on the client computing device; by the code segment, generating 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; sending the second request to the remote server; receiving, in response to the second request, one or more of the resources specified in the second request; and rendering 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.