3.5.16 was the version in Squeeze, with Squeeze-backports having v10.0

It's Debian 6 squeeze (see original post), but the OP has the code names mixed up.

version -3.5.16

that is your problem right there

the user agent switcher plugin for ff 41 will never install on the antique version 3 of the browser

and you might have issues using the current instructions for manual editing of the "about:config" string on such an old browser

upgrade !

i have firefox 41 running on a 15 year old p4 CPU-- mind you with all the scripting on web sites i MAX 100% the CPU for about 20 to 40 seconds and many web sites .

running ScientificLinux 6.7 and using a 15 year old 3d card

so your i3 cpu WILL handle deb 7.8 just fine

Well my solution of a user.js will still work - but I agree.

8.0 should still even work fine depending on which desktop one were to try to use.

right, i confused squeeze (debian 6) with wheezy (debian 7).
bloody hell, even wheezy is oldstable these days!

so, dear OP, there can only be one answer to your question:

install a current system.

if you need help with that, please open a new thread.

My fault. I confused them myself. In my original post I said I was using Debian 6. I should be using 7 but the last time I had to
re-install I appear to have used the old Squeeze CD instead of the Wheezy CD. Thanks for all the help.

I will sign off this thread and if I can wi=ork out how, mark it as solved.

I will start a new thread about installing Jessie on i3. I might see if I can do it with an Nvidia card in place.

Thanks again

Alaric