You're missing the point - there is no 1px gif, or hidden link. The only place that you can find the link is in the robots.txt file, and it's set to Disallow:
So if you're a "bad bot", you'll go to /blackhole/ looking for juicy stuff, and get banned. If you're Google you won't follow it (or he has a whitelist) and if you're an end user you won't even see it.
Edit: Ah, my bad. He does put a link to it in his footer.
http://perishablepress.com/robots.txt
So if you're a "bad bot", you'll go to /blackhole/ looking for juicy stuff, and get banned. If you're Google you won't follow it (or he has a whitelist) and if you're an end user you won't even see it.
Edit: Ah, my bad. He does put a link to it in his footer.