[JohnTHaller]

You're welcome. Based on my testing, I think you don't even really need a detailed chart, just a compatibility list. You'd be safe listing it as compatible with:

Mozilla Firefox (desktop and mobile)

Google Chrome (desktop and mobile)

Chromium

Internet Explorer 9 and later

Opera (desktop and mobile)

Safari (desktop and mobile) [this is an almost-positive guess but test to be sure]

You could then work backwards a bit on version numbering, trying older versions until you see where it breaks. You could put Firefox 31+ for now (since I tested 31 ESR), but that would be misleading since I'd wager it works quite a ways back on Firefox. Same with Chrome, Opera, and Safari. You could even just leave those versions off as users generally have the latest version of Firefox, Chrome, and Opera. Safari is another story since it's OS-tied like IE is, so you have a lot more users using an outdated version of desktop Mac OS X's Safari than outdated Firefox or Chrome users on the same OS versions. Leopard users are stuck on Safari 5.0.6 and Lion users are stuck on Safari 6.1. If you can get your hands on really just those two versions to double check, you'd be set and could list it as Safari 5+.

I may test back a bit as I'm playing with using Skeleton for an older site using Drupal with a single-page theme. I can drop you a note if I do.