1. A computer-implemented method comprising: by a computer system comprising one or more server computing devices, wherein individual server computing devices of the one or more server computing devices comprise a processor and a memory storing computer-executable instructions, retrieving a page of a content site; generating a preview representation of the page, wherein the preview representation comprises a screenshot of at least a portion of the page and markup code, and is at least partially optimized to reduce a loading time, such that a user-perceived loading time of the page is reduced; storing the preview representation of the page in a cache of the computer system; and subsequently, responding to a request for the page from a user device separate from the one or more server computing devices by at least delivering the preview representation of the page to the user device for temporary display on the user device, wherein the markup code of the preview representation causes the user device to (1) retrieve from the computer system, and display, at least the screenshot, and (2) transmit to the computer system a follow-up request for the page regardless of whether a user interacts with the preview representation; and responding to the follow-up request for the page by sending to the user device a non-preview representation of the page, said non-preview representation based on page content retrieved by the computer system; wherein the markup code causes the user device to temporarily display the screenshot while loading the non-preview representation of the page.