The purpose of this script is twofold: To show the perceived performance enhancements of pre-cached images, and To show how to script continually rotating images. When this page loads, it automatically pre-caches four images that are immediately available in the right-hand pane. The idea here is that as long as the visitor is waiting for a page to load, all the images may as well be downloaded up front, allowing for instantaneous image access thereafter. Activating the checkbox turns on a function that continually cycles through all pre-cached images at five-second intervals.