The Bitcoin mining signature generator functionality on btcstats.net has been shutdown.
The usefulness of this functionality dropped significantly when the BitcoinTalk forums disabled signature images and then subsequently made avatar images static. As a result, I decided to remove this functionality and stop paying the monthly hosting fees (this static web page is hosted on a free web host).
That said, I recognize that a small minority of people were using this signature images on other forums. While I'm not willing to continue to support this functionality just for that small group, I have made the source code freely available in case one of them wants to host this functionality themselves.