After you vote the button changes to [-1] and this means you can click it to withdraw your vote.
The text next to the button will show "No votes yet", or the number of votes received.
I am not implementing a down vote like other sites. You can vote +1 to show satisfaction with the post, approval, support or similar things.
This button will only show if you are logged in.
Obviously "ANSWER" is still used to set a reply/ies as the answer(s) to a topic question.