Some basic rules of thumb for designing for video

1. Save your images as 24 Bit RGB Color at 72 ppi (dpi).
2. Design your image file at 720x540 for NTSC graphics and resize down to
   720x486 for final output. (square to rectangular pixel adjustment)
3. Design your image file at 768x576 for PAL graphics and resize down to
   720x576 for final output. (square to rectangular pixel adjustment)
4. A pure white background will flicker on the television, and may cause
   text to flicker. Use an light grey/off white (234,234,234) colored
   background.
5. Use maximum R, G, B values of 234 or less.
6. Run Photoshop's NTSC video filter on your graphic for it to bring colors
   back into "safe" range.
7. Action Safe is 90% of your screen size and is considered safe for
   elements other than text that still needs to be seen.
8. Title Safe is 80% of your screen size and is considered safe for all
   text and elements that "must" be seen.
9. Account for the Interlaced Scanning found in NTSC and PAL television
   sets. To avoid flickering, make sure all fine lines are at least 2
   pixels wide and that any width is defined in multiples of 2 pixels.
10. 24 point fonts are best for television readability. A 14 point font,
    bold, is the absolute minimum size to use.
11. Anti-alias all text to avoid sharp edges.
12. Leave around a 25 pixel border from the edge of the graphic so that any
    element doesn't appear exactly at the edge of the screen.
13. Look at your work on a native video monitor (in addition to the computer display) to see how it looks on a television used in someones home. What you see on your monitor will most likely look better then what someone will have on their home TV.