iDVD: How to Determine TV Safe Area
The outer edge of your DVD menus and movies may not be visible on certain television sets.
For this reason, iDVD places buttons inside this outer edge (an area known as the "TV safe area").
To see the TV safe area for your project, choose Show TV safe area from the Advanced menu. A shaded area appears on the screen. The area that is not shaded is the TV safe area.
The TV safe area varies from television to television. The TV safe area displayed in the iDVD window is only an approximation.