[randomfool]

Latest release version of major browsers (Chrome, IE, FF, Opera, Safari).

Have a mobile version which tracks mobile browsers.

Once the HTML5 term was dropped (because it's a living spec), it's impossible to refer to any meaningful feature set. Of course it's all HTML, but there's so much variance in what's supported and what is not. If I can then say 'HTML 2011', that means HTML which was supported by RTM versions in 2011.

A variation on this would be to say that rather than referring to the latest RTM version of browsers, 'HTML 2011' would refer to the subset of HTML which can target 80% (or something) of worldwide users.

[netcan]

I like it. Something users can intuitively understand. Even if they need to be directed to it to find out.

"You need a browser that supports Web 2010 or higher to use this app."

On the other side, it would help users pressure webapp developers that aren't supporting their specific device / OS version.

"My browser is 2014. Why isn't this working." would be hard for customer service to BS around.

THe downside is that even if most of the browsers being used support some 2015 feature now, it would be hard to justify using it in 2013.