I'm not sure about what you mean by "the only distro that fit my laptop" since most of the issues are kernel related.
The latest Slackware release is 14.1.
You can get it easily by picking a direct download or a torrent download.
I advise you to use the "torrent way" since there's plenty of seeders for this release.
Download links can be found here : http://www.slackware.com/getslack/
Now regarding Firefox, the current version shipped with 14.1 is the 24.1.0 ESR
As you see, it's not a "cutting-edge" version but Slackware is not a Rolling Release meaning that everything is developped to provide the end user, a stable system.
From what I see in your profile, you are new to Slackware.
Reading the slackbook is good way to get started with Slackware.
It's included on the DVD iso.
Once you feel more confortable with the distro, you might fiddle with the source repository in order for you to adjust the packages of the distro to your liking.
Welcome on LQ and on Slackware