Newgrounds Wiki: Experience Points
Much like a traditional role playing game, registered users may acquire experience points and gain levels resulting in higher status. This is done by voting on five games and/or movies per day, which results in a deposit of ten experience points. You can only log ten points per day, there are no exceptions.
Experience points add weight to your votes. Users with an abundance of points will have the strength of multiple voters and can hurt the movies they hate or help the movies they love. Remember, you must be logged in for your voting power to be augmented!
Experience points also unlock secrets on your account page.
When the system was introduced in 1999, users could vote on each unique submission once daily. This meant you could return to Newgrounds on a daily basis and upvote the content you liked, or downvote the content you disliked. This resulted in a habit of "zero bombing" that was frowned upon and resulted in many discussions about the voting system.
In 2015 the voting system was changed to allow only one vote per unique submission.