Mozilla released Firefox 2.0.0.8 less than two weeks ago, and it is already time for Firefox 2.0.0.9. According to the Mozilla Developer Center, several important security fixes were rolled back while applying the 200 or so fixes that went into Firefox 2.0.0.8.
In a nutshell, this means that you shouldn't expect anything new from Firefox 2.0.0.9 if you are already running 2.0.0.8. That being said, you really need to go ahead and upgrade to the latest version to ensure you aren't susceptible to these old security issues.
[...] this month to address problems introduced in Gecko 1.8.1.8. This sounds like the same reason why Firefox 2.0.0.9 was released. If you haven’t already, you should take this opportunity now to update to the latest [...]
[...] released Firefox 2.0.0.8, they inadvertently rolled back some vital security fixes and where forced to release Firefox 2.0.0.9 very quickly. With the recent release of Firefox 2.0.0.10, a bug was introduced into the [...]