I've upgraded LMDE, but I still have Firefox 3.6.8, when I think I should have 3.6.11.

Why don't I have the latest version? I don't want to change to an unstable branch, but I do want the latest versions of the software. How come I can get 3.6.11 in Ubuntu, but only 3.6.8 in LMDE?

Because they are different distributions with different developers. LMDE currently is maintained by much fewer people than Ubuntu.

Debian Testing, on which LMDE is based, is still using an older version of Iceweasel (Debian's version of Firefox). When "Squeeze" goes to Stable, the new Testing version will be newer.

LMDE isn't using Iceweasel, it uses Firefox from the LMDE-repository.

So if I install Iceweasel(which is very similar to Firefox) in LMDE, I will eventually get a newer version, when testing is unfreezed?

You don't have to use the one provided by Mint - you can download a tar.gz from Firefox for Linux and install that. I'd recommend installing in a separate directory from where Mint's packages install. You'll need to modify your associations to point to the new location in desktop. You'll also need to be sure you link in any plugins (e.g. java, flash) to the new location so they're available to users.

Could you point me to more information regarding the linking of plugins?

From the Mozilla support site doing a query for "linking plugins" returns this list:
http://support.mozilla.com/en-US/sea...inking+plugins

Also you might want to look at this post for Java plugin specificially:
http://www.linuxquestions.org/questi...-3-6-x-825409/

An older post on installing Firefox tar.gz:
http://www.linuxquestions.org/questi...8/#post3191603

That was written for 2.x but the principles should apply for 3.x.

P.S. Once you install from tar.gz you can actually use Firefox's help - check for updates to update Firefox - you just have to remember to do it logged in as root as user's can't update for obvious reasons.

LMDE is, as the name says, based on Debian, so you can use every Debian repository you wish. I for my self use Iceweasel 3.6.11 from the experimental repo, and you can even get Iceweasel 4 beta from it. This way is, in my opinion, more recommended, because you get your updates with the regular system updates, instead to do it manually with the tar.gz.
Only thing you have to learn about using other repos is pinning

TobiSGD, thank you very much.

Pinning seems like it will be a much better option than installing it from tar.gz.

Except you get updates faster after the tgz install. I updated to 3.6.11 on my CentOS install a few days before RedHat released a package for the new security vulnerability. (Since CentOS is downstream from RHEL it would take even more time to get the fix on it.) Since LMDE is said to be downstream from Debian you'd see similar delays.

LMDE uses debian testing repositories. The mentioned experimental repository is way faster. But I see the main advantage of using a repository instead the tar.gz in the fact that you don't have to keep your eyes on Firefox releases yourself and all updates will come automatically. If one wants to or must be so up to date that he can't wait a few days to get the new version then of course the tar.gz solution suits the one better.

Once exploits have been released in the wild it is sometimes better to not wait. There are some security updates that don't really affect some of my systems due to either low or no visibility of them so I don't care. Other security issues need to be addressed rapidly. Each to his own - I don't use LMDE but find that using the tgz version of Firefox makes me more comfortable on the system I use daily to access the web. Note that the tgz method only requires the special steps first time it is setup - after that the Firefox updates do it all in the background as they do on Windows. chacun à son goût.

The new LMDE comes out in December, it will have all the new software with it

Open a terminal and type:

Hope this helps.