One thing that would be important to ensure accurate numbers is making sure the tracking image isn’t cached. We should send back the following headers:

Cache-Control: private, no-cache, proxy-revalidate
Pragma: no-cache

So in core/Tracker.php, maybe do something like:

protected function outputTransparentGif()
{
if( !isset($GLOBALS[|| !$GLOBALS[‘DEBUGPIWIK’](‘DEBUGPIWIK’])) )
{
$trans_gif_64 = “R0lGODlhAQABAIAAAAAAAAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==”;
header(“Content-type: image/gif”);
header(‘Pragma: no-cache’);
header(‘Cache-Control: private, no-cache, proxy-revalidate’);
print(base64_decode($trans_gif_64));
}
}