WebTV has a whole site dedicated to making your sites work in their browsers. They have even developed a WebTV emulator that you can use on your computer. To get this and other tools go to: http://developer.webtv.net
This is your single best resource for developing WebTV compliant sites and applications.
For many site developers, no amount of redesign will make a web page friendly to WebTV. In such cases, it's probably smartest and easiest to just dodge the issue -- by making up special pages that *are* suitable for WebTV, and redirecting to them.