Not to downplay Matt's response, but I've used the site on Firefox (mac/pc), IE 8, 9 and 10, 3 different builds of Chrome (mac/pc) and Safari. They all seem to work. I've also tested it on Safari (iphone), Dolphin (Android), and various other mobile browsers.
I don't know if you'd call it testing per se, but they've all seemed to work fine. I'm a little bit of a browser skitzo.
Looks like the only mainstream one I'm missing is Opera, but seriously...who uses that?