OK I think I know what your talking about...here comes Zeros's' ultimate explanation (me being smart haha Laughing )
Ok a warn thing is in use for admins and moderators of the board. If they feel you have been abusing the board they will warn you, when you get to 90-100% warn (or on some boards 4/5 blocks), you will be sent an e-mail (maybe not...) telling you whats going on, this will also limit your board usage (i.e. how many posts a day and what you are allowed to post) other users can warn you also but it will not take affect untill a moderator or admin has confirmed it. Thats about all I have to say, but if you want a firm explanation ask an admin or moderator (i.e. Spyder or Xorlax) B)