What browsers are supported by Marketpress?

Quick question for ya this morning!

We have marketpress installed on http://www.dearhandmadelife.com as a way for people to pay for upcoming craft show booths and for the most part, it's working great.

BUT - out of the hundreds of good transactions, we've had a couple of people email saying they have problems with entering the shipping address, specifically with the states dropdown.

Both times I've suspected user error, since there have been SO MANY good transactions - but the second one that came through with the states dropdown yesterday, the guy specifically said he was on an older computer. I reached out and asked what he was on and how he was browsing, and he said a mac with safari 4.05

Is there documentation somewhere on what browsers and versions of browsers are supported by marketpress that I can call out on the site, like you need to be rockin safari version xyz, chrome abc or whatever to pay for your booth?