Rather than grading browsers, we grade components. This provides each browser with the best experience it can handle. We use Strong Progressive Enhancement.
Cutting the Mustard
They picked those criteria based on the things the features that their app used. If you cut the mustard in your own project, you should test for features that you’ll be using. Modernizr can be a useful tool to use for this.
There are levels of optimisation to apply. Your site should support every browser, but the amount of time you spend optimising for particular browsers and feature sets should depend on your audience.pe