[jrockway]

This means that you need some sort of comprehensive integration that tests all corner cases of features you use. You certainly can't rely on the browser vendors to implement every feature perfectly according to spec with no bugs. So you have to test it yourself. Most people test their app, see that it mostly works, and then declares the browser supported. That's why we get these things like "please use browser X"; it's what the developers checked the corner cases on.

[boring_twenties]

Sure, that sounds reasonable but even my bank manages to just display a warning at the top which I can click away for the rest of the session. So when something like Skype or Slack just outright refuses to work, it's quite some nerve they've got there.