Still using Firefox 3.6? That might not last for much longer. ComputerWorld reports that Mozilla will roll out Firefox 12 as an automatic update to Firefox 3.6 some time next month. In short, unless you disable the browser's auto-update feature, you're going to wind up running the latest release.
This plan doesn't come entirely out of the blue. As ComputerWorld points out, Firefox 3.5 received the same treatment last year. And as of last Tuesday, Firefox 3.6 is no longer officially supported by Mozilla—the last security update for it came out on January 31. If new vulnerabilities are uncovered (or exploited) in the future, they'll go unpatched.
There is an alternative for those who still need support but don't care for the breakneck release cycle of recent Firefox versions. That alternative is called Firefox Extended Support Release, and it has a 54-week life cycle during which only security updates are pushed out. Right now, the browser corresponds to version 10 of Firefox, which was released last December. Mozilla aims Firefox ESR at "groups who deploy and maintain the desktop environment in large organizations such as universities and other schools, county or city governments and businesses."
I'm sure some users will moan and kick and scream about the change. They might even have good reasons to. Still, I have to give Mozilla credit for not indulging stragglers too much. Old browsers are bad for the web. They're less secure, less compatible with new web technologies, and harder to support for web designers and programmers everywhere.