I've noticed that Firefox 3.0.13 has several problems displaying Glitch pages correctly (pages which work properly in Safari):
On glitch.com/join/ clicking on the Facebook button does nothing except generate a "loading" graphic. Clicking on "give us an email address" takes you to a page (http://glitch.com/join/#) where there is no place to enter an address.
beta.glitch.com/vanity/ loads nothing but a blank screen.
beta.glitch.com/wardrobe/ allows you to see the clothing, but the "Test" function does not work.
beta.glitch.com/ does not show a picture of your avatar; there are also no other pictures, only text updates.