Facts like these always drives me crazy... these companies (namely Microsoft, but I guess Google/Mozilla as well a bit) have huge teams and resources, and can't build a browser that follows specs that have been hammered out only after years of work.
There's a reason why some bodies ship a reference implementation with the standard. Sometimes what's specified is infeasible, or even impossible (if the spec contradicts itself) to implement.
That doesn’t mean they can’t be expected to support a meaningful subset. Honestly I don’t even know what they’re thinking here: they have no real alternative.
