New Lock Icon in Upper Right Corner

I have a question if anyone could help me out! I have the 3GS with the downloaded OS 4 software. ever since i updated with the new software there is this new icon in the upper right corner, it looks like a lock but it has a circle with an arrow at the end surrounding it, i think it means its locking the featuring to where if i turn my phone horizontal the screen will also turn horizontal, the problem is i cant figure out how to disable the lock. can anybody help?