Well, you're comment made me aware I'd better restart my iceweasel session, I'd already upgraded from 29 to 31, but was running old code. And then I found out I'll probably have to reboot, as firefox/iceweasel tries to pull in nouveau-based drivers... and I'm running the binary-blob nvidia drivers.

So, still no webgl, but with any luck xorg will come up with accelerated 3d on next re-boot - and webgl will work too.

I do wish more hw companies would just release free and open drivers...

This particular rig is a hand-me-down -- next gpu will be radeon, among other things for their efforts to be a better driver-citizen than nvidia. Even if for a certain set of configurations, nvidia has delivered better actual hw performance under Linux, for certain fixed configurations.