1. Apparatus, comprising: one or more hardware processors; computer memory associated with the one or more hardware processors; computer program instructions held in the computer memory and executed by the one or more hardware processors to change the content of an object, in response to a request for the document from a client, the computer program instructions comprising: first program code operative asynchronous to, and prior to the request from the client, to analyze at least a portion of the object to identify at least a predetermined characteristic and, in response thereto, to create one or more transformation instructions corresponding to the characteristic; second program code operative to store the one or more transformation instructions prior to the request from the client; and third program code operative upon receipt of the request for the object to modify the object based on the one or more transformation instructions previously stored, and to return the modified object to the client in response to the request for the object; wherein the third program code operates in a request and response processing flow between the client and an origin server that publishes the object, and the first program code operates externally to the request and response processing flow between the client and the origin server.