There is no reason why a page should not update immediately if you force your browser to refresh from the domain (control-refresh in IE and shift-refresh in Netscape). Remember, the transparent proxy is not the only place for caching. Copies are saved in your computer's cache for quick reference, and there may be any number of cache operations at any point in the path from the Customer to that site's server.
If you updated your site but still can't see it updated, your computer cache is most likely refreshed. You need to please (ctrl +f5) or need to delete your internet cache, history, and cookies. After doing this, your pages will be showing updated immediately.
