diff --git a/appimage.php b/appimage.php
index 4962836..1a59075 100644
--- a/appimage.php
+++ b/appimage.php
@@ -6,14 +6,78 @@
 include("path.php");
 require(BASE."include/"."incl.php");
 require(BASE."include/"."screenshot.php");
+
+/* an image doesn't have a link, so a cookie makes no sense */
+header("Set-Cookie: ");
+header("Pragma: ");
+
 if(!$_SESSION['current']->hasPriv("admin") && $_REQUEST['queued'])
 {
-    errorpage("Insufficient privileges.");
-    exit;
+   errorpage("Insufficient privileges.");
+   exit;
 }
-$oScreenshot = new screenshot($_REQUEST['id'],$_REQUEST['queued']);
+if ($_REQUEST['REQUEST_METHOD']='HEAD')
+{
+   /* WARNING! optimization of logic in include/screenshots.php */
+   if (sscanf($_REQUEST['id'],"%d", &$iId) < 1)
+   {
+      errorpage("Bad parameter");
+      exit;
+   }
+   $sQuery = "SELECT id FROM appData 
+              WHERE id = ".$iId."
+              AND type = 'image' LIMIT 1";
+   if (!($hResult = query_appdb($sQuery) &&
+         $fImage = fopen(appdb_fullpath("data/screenshots/".$iId), "rb")))
+   {
+      header("404 No such image");
+      exit;
+   }
+   $fstat_val = fstat($fImage);
+   $iModTime = $fstat_val['mtime'];
+   $sMagic = fread($fImage,8);
+   fclose($fImage); /* don't leave the fopened image open */
+   /* identify what kind of image this is, if we can't identify it */
+   /* we should report that its a bad image */
+   if (strcmp("\x89PNG\r\n\x1A\n",$sMagic)==0) 
+   {
+      header("Content-Type: image/png");
+   } else if (preg_match("^\xD8\xFF^",$sMagic)) {
+      header("Content-Type: image/jpeg");
+   } else {
+      header("500 Bad image format");
+      exit;
+   }
+   header("Cache-Control: public");
+   header("Expires: ");
+   header("Last-Modified: ".fHttpDate($iModTime));
+}
+$oScreenshot = new Screenshot($_REQUEST['id']);
+
+/* at this point, we know that .../screenshots/$id and
+ *  .../screenshots/thumbnails/$id both exist as normally 
+ *  they would both be created at the same time. */
+$fstat_val = stat(appdb_fullpath("data/screenshots/".$_REQUEST['id']));
+$iModTime = $fstat_val['mtime'];
+
+header("Cache-Control: public");
+header("Expires: ");
+
+/* if the browser is asking if the file was modified since a particular date */
+/* and the date is the same that the file was modified, then we can report */
+/* that the file wasn't modified, the browser can used the cached image */
+if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && 
+    $iModTime == pHttpDate($_SERVER['HTTP_IF_MODIFIED_SINCE']))
+{
+   header("HTTP/1.0 304 Not Modified");
+   exit;
+}
+
+header("Last-Modified: ".fHttpDate($iModTime));
+
 if(!$_REQUEST['thumbnail'])
     $oScreenshot->oScreenshotImage->output_to_browser(1);
 else
     $oScreenshot->oThumbnailImage->output_to_browser(1);
-?>
+
+?>
\ No newline at end of file