Something I love about the design of the web standards: It takes next to no effort from browserdevs to implement reasonable fallbacks for features they've yet to implement! If they ever will.
We call this "graceful degradation". It makes things easier on (patient) webdevs, & on the browser devs.
JS btw does not have this. It throws errors upon encountering unknown APIs, making it the webdev's problem. HTML & CSS don't.
