Some of the major rules changes for 2008 include the following:

• A chop block is defined as a high-low or low-high combination block by any two players against an opponent (not the runner) anywhere on the field, with or without a delay between contacts
• The Play clock is set to 40/25 seconds depending on these circumstances

  40 Seconds
  

  Dead ball in bounds
  

  Dead ball out of bounds
  

  Incomplete Pass

  
  

  25 Seconds
  

  Penalty Administration
  

  Charged Team Timeout
  

  Media Timeout
  

  Injury Timeout
  

  Measurement
  

  Change of Possession
  

  Try for Extra Point
  

  Start of each period
  

  Start of possession series in Extra Period
  

  Instant Replay Review
  

  Other administrative stoppage

  
  
• When a ball carrier, a fumble or a backward pass goes out of bounds, the game clock will start on the referee's ready-for-play signal when the ball is placed at the appropriate spot. (Exception: Within the last two minutes of each half thegame clock starts on the snap.)
• All players are prohibited from grabbing the inside back collar of the shoulder pads or jersey, or the inside collar of the side of the shoulder pads or jersey, and immediately pulling the runner down. This does not apply to a runner who is inside the tackle box or to a quarterback who is in the pocket.
• No player shall twist, turn or pull the face mask or any helmet opening of an opponent. It is not a foul if the face mask or helmet opening is not twisted, turned or pulled No more 5 yard penalty; 15 yards on all fouls of this nature.
• No player shall initiate contact and target an opponent with the crown of his helmet. When in question, it is a foul.
• No player shall initiate contact and target a defenseless opponent above the shoulders. When in question, it is a foul.
• While the ball is in play, coaches, substitutes and authorized attendants may not be in the restricted area between the sideline and the coaching box or on the field of play. PENALTY- First and second infractions: Delay of game for sideline interference, Five yards from the succeeding spot. Third and subsequent infractions: Unsportsmanlike conduct for sideline interference, 15 yards from the succeeding spot.
• Replay can now review field goals. This includes field goal attempts only if the ball is ruled (a) below or above the crossbar or (b) inside or outside the uprights when it is lower than the top of the uprights. If the ball is higher than the top of the uprights, the ruling may not be reviewed.
• The Instant Replay Official may correct an egregious game-clock error. If a head coach's challenge is successful he retains the challenge, which he may use only once more during the game. Thus a coach may have a total of two challenges if and only if his initial challenge is successful.