1. A method of providing content to a device according to Hypertext Transport Protocol (HTTP), the method comprising: receiving an HTTP request for a first content object; identifying a content operation identifier that identifies a corresponding second content object determined as relevant to the first content object by a predictive caching operation, the content operation identifier including a directive for prefetching the second content object as a content operation distinct from presentation of the first content object by the device; and sending to the device an HTTP response to the HTTP request, the HTTP response including the first content object and the content operation identifier, enabling the device to perform the prefetching of the second content object based on receipt of the content operation identifier and distinct from the presentation of the first content object; wherein the sending step includes adding to the first content object a content operation tag that specifies the content operation identifier including a directive tag specifying the corresponding content operation to be performed by the device and an object identifier that specifies a location of the second content object.