- Scoring -

Points are awarded to the opponent for any of several errors in play:

• Allowing the ball to bounce on one's own side more than once.


• Double hitting the ball. Note that the hand below the wrist is considered part of the racket and making a good return off one's hand or fingers on the racket-holding hand is allowed, but hitting one's hand or fingers and subsequently hitting the racket is a double strike and an error.


• Allowing the ball to strike anything other than the racket (see above for definition of the racket)


• Causing the ball not to bounce on the opponent's half (i.e., not making a "good" return)
  Placing one's free hand on the playing surface or moving the playing surface
  Offering and failing to make a good serve (i.e., making a service toss and failing to strike the ball fairly into play)


• Making an illegal serve: (e.g., one preceded by a player's hiding the ball or his failing to toss the ball at least 16 centimeters (six inches) in the air).


• Hitting the net with racket or any body part.


• By volleying the ball (not allowing the ball to bounce on your side)

source: wikipedia.org