Rules of Tennis 2010. Published by the International Tennis Federation.
11. BALL IN PLAY

Unless a fault or a let is called, the ball is in play from the moment the server hits the ball, and remains in play until the point is decided.
12. BALL TOUCHES A LINE
If a ball touches a line, it is regarded as [...]

[Calgary] Three years ago, Racquet Network members asked network administrators to drop general membership fees and rely instead upon advertising revenues to finance racquetnetwork.com.
At the time, dozens of members argued vehemently that ad revenues would more than make up for the loss of general membership fees. They said that offering free memberships would attract thousands [...]

Rules of Tennis 2010. Published by the International Tennis Federation.
10. CHANGE OF ENDS
The players shall change ends at the end of the first, third and every subsequent odd game of each set. The players shall also change ends at the end of each set unless the total number of games in that set is even, [...]