I popped into a question today was trying to give something an up vote but I clicked on the wrong reponse so I tried to take it away but instead of taking it away it gave it a down vote which really wasn't fair, but the response definitely did not deserve an up vote. Is there anyway to set it back to neutral and apply no vote? I am assuming since I have navigated away from the page the votes would just stand but it would be nice to know for a future incident that I hope to never have again. :|
Within a limited time window, you can click the same arrow and it will undo the vote. At this point it will probably tell you it's too late.
You can change your vote again if the post is edited. Some people with edit privileges will make a trivial edit (adding a space or something) in order to do this; if you don't have that privilege yet, you can ask the author to make such an edit. I'm sure s/he'll be happy to oblige if it's to get a downvote removed.