That looks different depending on the feature,
but can often include new tests
for the @supports conditional rule.
So how do these CSS feature queries work,
what happens when we add new syntax to the @supports rule,
and anyway: what is the opposite of an unknown?
Working on a new CSS feature like Container Queries, one of the most important considerations is to ensure a “migration path” – a way for developers to start integrating the new code, without breaking their sites on legacy browsers.
Support (Not) Unknown
Adding Container Query tests to CSS @support
Repost from OddBird.net
