Use different font when Zooming in in Firefox

When I zoom in using Firefox, I would like to change the font used on the site to Georgia because it looks better in larger size. Is there a Firefox extension or javascript I can use to make this happen? O开发者_开发百科r attach the Zoom keyboard hotkey to a user defined css file maybe?

I think the difficulty you're going to run into, unfortunately, is that it is difficult, if not impossible, to tell what zoom level the browser is at using straight up javascript.

That said, the flash plugin, which most people have, seems to have a way (demo).

If you can get a change in that value to trigger a function (not sure if that's possible, but I'm guessing it is), you can just set that function to change the font-type of class foobar to Georgia.