Jason revisits some cutting-the-mustard techniques, as started by the BBC and refined by Jake. This kind of feature-testing is indispensable for progressive enhancement.
Personally though, I’m still uncomfortable with the assumptions baked into equating particular features with particular browsers …maybe I’ve known PPK too long.
I much prefer to cut the mustard on a case-by-case basis by feature testing the actual APIs I’m about to use in a script. I realise that might be harder to scale, and it’s more verbose, but it’s the only way to be absolutely sure.