Reducing Latencies in Web Page Rendering

A page structure may be used to begin validation of an embedded resource prior to the time a browser issues a request to validate the embedded resource. A page structure includes information indicating one or more embedded resources in the web page and, in some implementations, its corresponding cache characteristics. The page structure may be used to generate a validation message that indicates resources to be validated. The validation message may be sent to a server at substantially the same time that the browser begins rendering the web page. The server can then begin validating the resources indicated in the validation message by sending validation requests to an origin or other server storing the embedded resources. The server then may send the validation responses back to the client computer executing the browser so that the validation responses can be used to satisfy corresponding validation requests generated by the browser.