This was a thought I've been pondering over for a while now. I know in Oblivion if you went to jail, a random skill would decrease by a certain amount. Now im starting to wonder if this happens in Skyrim also, or if its only in Oblivion.

They supposedly do but I've never been in jail long enough to find out.

They go back to 0% progress

Well crap, I was hoping they wouldn't since Im getting tired of paying for the bounty. Guess Ill just choose to go to jail and escape.

I dunno, when I go to Jail I quickly escape...

with Lock picking, a muffle spell, and an invisibilty spell, the jails may as well be made of tin...

And now I have the song "Big Rock Candy Mountain" stuck in my hand... thanks a lot OP....

Yuppers, but only if you choose to 'serve your time.'

Skill level never goes down, though. For example: If your light armor is at 82, it will stay at 82 regardless. But all progress toward level 83 is lost.

Yup this.

The progress towards your next level will reset to zero.

This was fixed in skyrim so you couldn't keep leveling up past the level cap.

However with the last patch patch you can level up pretty much as high as you want,if you have that kind of time.

It starts out as a couple of skills decreasing, longer you're in, more range of skills decrease.

i wouldnt suggest that because if you escape you still have your bounty.

And no skills dont decrease they just lose their accumulated progress.

The skill level itself doesn't drop when you do a stent in jail, but the progress to the next level is lost. Where in I mean that if the level progression bar in one-handed is 3/4 full and you are just about to level up, that progress will be lost IF you are sent to jail. But the skill itself doesn't drop, not like in Oblivion.