Are you having any luck changing the font sizes in WebTV? My emulator version of it doesn't respond to my attempts to decrease the size of the font in the menu. But it's working fine for any other browser.
Keep in mind (I'll make this more apparent later) that you're not limited to using "100%" or "80%" or any percentage. You can also specify point size, as in "12pt" or "8pt". Well, "you" in the global sense. I'm not sure you personally will be able to take advantage of that on WebTV.
As you probably know already, one of the neatest things to me about this is that if someone doesn't like the size or color or emphasis or font used somewhere on the site, they can change it themselves to whatever they like.
Even WingDings, apparently. LOL