Didn't work here, just a bunch of colored squares on Safari, Chrome or Firefox. The latter actually managed to hang my machine. I could ssh to it but kill -9 wouldn't terminate Firefox. Had to force reboot the machine, haven't done that in years. Amazing and scary, this WebGL thing is. iMac 2011, latest OS Edit: worked on MacBookAir
Sounds like some dodgy graphics driver on your old iMac
I object that qualifier, if you don't mind :)