Yeah, I've been seeing this in the terminal when I run from the command line too. It was just a minor bug in the mechanism that tests for accelerated graphics support on Linux. (unfortunately, you need a fairly new version of your distro in most cases; e.g. Ubuntu 10.04.x LTS doesn't have support but newer versions do) Basically it's a warning the test is getting that tells it that part of what's needed for support isn't there, but it showed it anyway. It's been fixed for Firefox 9+ but in the meantime don't worry about it.