Last major update: January 2002
Last minor update: April 2003.
Discussed version: Viewer 2.6
Viewer 2.8 has been released, but I haven't yet studied it.
WebTV is meant for browsing the WWW on a TV. It is currently owned by Microsoft.
WebTV is not a browser for a computer. Instead, it is meant to view web pages on a TV. Hence it has some severe limitations, the most important of which is that it has a small screen. It's been bought by Microsoft, which has redesigned the WebTV developer site. (Interesting details: the page is slightly too wide for WebTV, it is also not possible to click on some of the links in the Viewer).
I don't have a real WebTV, but I use the WebTV Viewer 2.6 to test my pages. As far as I understand the real WebTV is slightly better than the Viewer, so that everything that works in the Viewer should also work on WebTV. In addition, the real WebTV is automatically updated if there's a new patch or workaround, so that developers only have to worry about the latest version of WebTV.
WebTV has roughly the same CSS support as Explorer 3: piss poor. But I assume that they're working on it and that it'll become better in the future.
WebTV says it supports
document.layers but in fact it doesn't execute
any DHTML script, so I wonder why they bothered.
One interesting point is its treatment of popups. It used to treat them as new pages (since a TV by definition has only one screen), but now it appends the popup to the page that called it and scrolls down. Scrolling back up gives you the main page again.
Although it doesn't have a large market share, testing your sites in WebTV is useful, mainly because it teaches you not to assume every end user has a 1024x768 computer screen.