I accidentally voted a question down. I thought voting up once would help my accidental move look like never happened but instead it voted up the question. I, again, thought voting down would settle the things, but surprise surprise :) question was voted down. So did I miss anything or is there a way to undo a voteup or a votedown?
If you are within the 5 minute grace period, just click on the votedown button again to undo.
If the grace period has passed, either wait for the question to be edited, or edit it yourself to undo the downvote.