In my earlier post I mentioned that ShortStats is unable to track failed referrers due to the way it works. ShortStats relies on a single line of PHP being inserted into each page you want to track, which then triggers a PHP script which logs the request in the database. I realised shortly after I posted that an obvious way to track failed referrers would be to put a slightly different PHP fragment into the custom 404 page. This would then log the original request (rather than the request for the 404 page itself) into a new DB table and you’d have yourself a failed referrer. Perhaps I’ve found a little project for myself this weekend…