HTTP <META HTTP-EQUIV="pragma" CONTENT="no-cache"> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache, must-revalidate"> <META HTTP-EQUIV="expires" CONTENT="Wed, 26 Feb 1997 08:21:57 GMT"> <META HTTP-EQUIV="expires" CONTENT="0"> PHP header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); header("Cache-Control: no-cache, must-revalidate"); header("Pragma: no-cache");