It's a link which gives the user who owns the link 30 or so TC every time someone clicks it. It make your on.toribash link go here - http://on.toribash.com/
I'd like to remind you that advertising your on.toribash links on this forum is against the rules, and you can get infracted/banned for repeated posting of them.
So if I were to put one in my sig, and cover it up with... Oh, let's say "I dare you, Click me" would that work, or is it against the rules?
Posting your on.toribash links in any way, such as like you stated, or through a picture (if you have toriprime) is allowed. Just make sure it's in your signature.