1. A method comprising the computer-implemented steps of: at an intercepting device, intercepting a Hyper-Text Transport Protocol (“HTTP”) response message that has been sent over a computer network from a provider server device to a requestor client device, prior to said HTTP response message arriving at said requestor client device; wherein the intercepting device is deployed on the computer network between the provider server device and the requestor client device, wherein the HTTP response message provides content and is addressed to said requestor client device and not to the intercepting device; based at least on the intercepted HTTP response message, the intercepting device determining what content is being provided by the provider server device in the HTTP response message; before the content is delivered to the requestor client device, the intercepting device determining whether the requestor client device is associated with any user of a first set of users or any user of a second set of users, wherein each user in the first set of users is required to authorize payment for the content, wherein each user in the second set of users is not required to authorize payment for the content; responsive to the determining that the requestor client device is associated with a user in the first set of users, the intercepting device sending the requestor client device a payment authorization request message; responsive to detecting that the requestor client device has authorized payment for the content, the intercepting device transmitting the HTTP response message from the intercepting device to allow the requestor client device to obtain the content; wherein the method is performed by one or more computer devices.