(*) Refresh is noticably slower than Redirect and causes a white flash in Firefox, Opera, Chrome and Safari mobile.
(**) Interenet Explorer reloads the image after a Post/Refresh/Get.
The image above should not reload from the server. However in Safari 5, Chrome 6 and Safari mobile on iOS 4 (and iOS 4.0.1) the image reloads from the server after a Post/Redirect/Get. This problem didn't occur on Safari mobile on iPhone OS 3.1.3. This appears to be a regression.
The Response headers sent with the image:
HTTP/1.1 200 OK Date: Thu, 24 Jun 2010 12:02:33 GMT Server: Apache Cache-Control: public, max-age=32140800 Expires: Fri, 01 Jul 2011 12:02:35 GMT Etag: "866-1276639825" Last-Modified: Tue, 15 Jun 2010 22:10:25 GMT Content-Length: 866 Content-Type: image/png