In general as regards SVG [and canvas in this case], not IE <=8 or Android <= 2.4, and some caveats (eg will need careful testing, as some JS/DOM APIs or rendering optimisations may not be present) with earlier versions of FF/Chrome/Safari & IE9/10
what about in a year? i bet you would list different browsers and versions. my point is, "modern browser" doesn't mean anything and it change as time passes
True, it should specify where support drops off really, it's not as if there aren't tools to automate the JS testing part of it if the time isn't there to thoroughly manually check. I've think maybe spent too much time assessing JS libraries & frontend stuff; after a while when you see 'modern browser' you mentally tick off where it's likely to be functional and accept/discount the guessed tradeoffs (maybe a bad habit)
