To see the TV safe boundaries for your project:
Make sure the menu you want to check is showing in the iDVD window.
Choose View > Show TV Safe Area.
A shaded area appears on the menu. The inner area that is not shaded is visible on most television sets.
If your project is widescreen, with a 16:9 aspect ratio, choose View > Show Standard Crop Area.
The area inside the boundaries is visible on a standard television screen.