Recently, I stumbled across a quote from a Mozilla developer about the tension inherent in creating standards:
Implementations and specifications have to do a delicate dance together. You don’t want implementations to happen before the specification is finished, because people start depending on the details of implementations and that constrains the specification. However, you also don’t want the specification to be finished before there are implementations and author experience with those implementations, because you need the feedback. There is unavoidable tension here, but we just have to muddle on through.
Keep this quote in the back of your mind, and let me explain how HTML5 came to be.