1. A method operating on one or more network devices for providing content over a network, comprising: receiving a request for a content object, wherein the content object includes at least one link to another content object; determining a cachability measure for the at least one link based on a weighted sum of probabilities of a plurality of different cachability criteria; determining a prefetchability measure for the at least one link based in part on the cachability measure and another factor associated with the other content object including lowering the prefetchability measure based on whether caching of the other content object causes a related third content object to be uncachable; and if the prefetchability measure meets a threshold selected to indicate when content objects should be prefetched, prefetching the other content object for use by a client device, wherein prefetching is further based on a combination of an attribute of the request at an Open System Interconnection (OSI) layer 3 or above and an authorization to use the link by a user associated with the request.