Today I started work on a TV compatible design. After a little research, there are some important considerations for Web TV.

1. Screen Dimensions for 4:3 are Width=560, Height=420.
2. Usable Space are Width=544, Height=372.
3. 48 pixels are taken up vertically (36 at bottom of the title bar from height) and 8 pixels on each side (total16)
4. No Horizontal Scroll Bar!
5. Can only view Flash 3 content, at the moment.
6. Because television is interlaced at 60 Hz, a one-pixel line will show only in half the frames (30 Hz).
7. Graphics are shrinked by 10%. So avoid graphics with small text/type.
8. Supports only 8-bit color (256 colors)
9. Keep text at least normal size (12 points). WebTV displays sans serif type regardless of what you typeset.
10. Javascript 1.0, Supports CSS & DHTML, but not XML & VBScript

For more info on Web TV check out the following
www.webtv.net
Authoring Web TV
Development Checklist
and
WebMonkey’s WebTV article