Six of them, and they fit on one screen on purpose. A board whose rules need a lawyer is a board that is hiding something.
Not a percentage. An entry with 41 up and 13 down sits at +28 and ranks above one with 24 up and 2 down, at +22: it convinced six more people, even though a smaller share of its voters liked it. A ratio would put a three-vote entry at 100% and hand it the top spot on its first afternoon.
Two entries on the same score are ordered by submission date, oldest first. Scores move and the board moves with them, several times a minute, but a tie is always broken the same way: nobody overtakes anybody by standing still.
Up or down, not both. Clicking your own thumb again removes your vote. Changing your mind moves the score by two, because you are taking one back and giving one away.
Vote on as many entries as you like, as fast as you like. On any single entry, one action per minute: voting, changing your mind and cancelling all count. Cancelling does not reset the clock, so there is no way to undo and re-vote your way around it.
You do not sign up, and there is nothing to sign up for. Your vote is tied to an anonymous identifier stored in a cookie. That stops double clicks, page reloads and second visits, which is most of the noise.
It does not stop somebody determined to clear their cookies and vote again. We are telling you rather than claiming a robustness we do not have. Voting is also capped at 20 per minute per network address, and submissions at five per hour. That is the whole defence.
The two columns of sponsor cards are sold. The ranking is not, at any price, and there is no arrangement to ask about. That single line is the entire reason this site exists: on a pay-to-rank board, first place goes to the largest wallet in the room, and the list stops telling you anything.
Every score, every count, every position. What stays private is who voted for what: publishing that would hand a map of active voters to anyone who wanted to imitate them.
Malware, scams and content that is illegal where it is hosted come off the board. Nothing else does. An entry you dislike has a downvote button.