Mozilla Firefox 26 is released and this is guide, howto install Firefox 26 on Fedora 20/19/18/17/16, Cent OS 6.5/6.4/6.3/6.2/6.1/6 and Red Hat (RHEL) 6.5/6.4/6.3/6.2/6.1/6 using YUM.
When it reaches the stable repositories, the fixes will be applied during your next system update.
(New versions of some packages and really old versions of others have not necessarily been tested together, after all.) If you're accustomed to using the Software Updater (Update Manager in older Ubuntu releases), go ahead and do that.
If you prefer to use the command-line: will upgrade packages that require the installation of new packages or removal of currently installed packages, so you should make sure to look at what it says it plans to do, before letting it proceed.
(If this is a recurring problem, read this for other possible solutions.)   Try starting Firefox or Sea Monkey in Safe Mode (see the linked article for details).
If the browser starts when you run it in Safe Mode, it's likely that an extension or, in Firefox 4 and above, hardware acceleration is causing the problem.
You should then delete the program folder for your Mozilla browser and run the installer you previously downloaded.