It's a simple letter substitution. The same letter is substituted throughout each puzzle. Solve it by trial and error. I've had a few people tell me they enjoy these, so I'm trying to update them more regularly, or at least more of them when I do.
Response is good.
I'm trying to update more often. I've also posted the answers for the last few that were here. I've also left them at the bottom in case you just got here, and the new ones aren't enough.