if (navigator.appName.indexOf("WebTV") != -1) // WebTV detected
   document.writeln("How do you like that WebTV?");
else // not WebTV
   document.writeln("When are you going to get WebTV?"); 

You can use this technique to redirect WebTV users to a WebTV-optimized version of your site. Furthermore, you can take advantage of this sniffer to overcome various bugs in the WebTV implementation of JavaScript.

People who read this tip also read these tips:

• The Screen Object
• Three-Way Browser-Independent Scripting
• Keeping the Prototyping Information
• Retrieving Event Location
• Owning an Element