Quote from WHATWG.
The WHATWG was based on several core principles, in particular that technologies need to be backwards compatible, that specifications and implementations need to match even if this means changing the specification rather than the implementations, and that specifications need to be detailed enough that implementations can achieve complete interoperability without reverse-engineering each other.
I teach web design. I write books on HTML5 games development. I host classes on mobile web and app development. I made animation with Adobe Flash (now Animate).