Yes you can do that but before you do that I recomend to you do the folowing:

• First update your Firefox to the latest version (it's 24)
• Clear your cookies and cache
• Check and see if your problem still exist

• Installing multiple different versions of Firefox.
• Opening a new instance of your Mozilla application with another profile
• Using multiple profiles - Firefox

As stated in my question, I am running lubuntu, a Linux OS. All of your threads seem to be Windows based. Clearing cache and cookies does not help. The gist of what you were getting at implies that I have to run 2 different profiles. I understand, in LINUX, this to mean logging in under a separate profile to get access to the other version. Or put simply, installing each in separate profiles. I'm not so sure that this would work as both would be using the same filing system. On my machine Firefox is located:: /etc/firefox. It might work if one installed to /etc/firefox1 and the other to /etc/firefox2. I'm not too sure how to create the correct path to each and whether or not, once fired up, Firefox wouldn't try to 'sort it out' it's own way. But I'm not that clever.

To run 2 different version of Firefox at the same time follow those steps.

1. You say that you are using 21 so lets download 24. Download it from here www.mozilla.org
2. After your download is complete extract the files of firefox-24.0.tar.bz2 on your Desktop.
3. Open a terminal and run firefox -p -no-remote. Profile manager will open.
4. Press Create new profile to the new window that will open click Next then give a name to your new firefox profile and click Finish and press Exit to close profile manager.
5. Now lets start new firefox (24) with the new profile. Type in your terminal ~/Desktop/firefox/firefox -p *profile-name -no-remote

  *profile-name = Type the name of your profile that you have create with profile manager on step 4.

I hope this helps you.

You need to use the -no-remote command line switch to open another Firefox instance with its own profile and run multiple Firefox instances simultaneously.

• http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile

• https://developer.mozilla.org/en/Mozilla/Multiple_Firefox_Profiles

Dear Sirs http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile:: this seems to me to be running the same firefox.exe under different names. NOT what I'm after. Creating a folder on my desktop and running the separate files from the command line might come closer. From my dabbling firefox seems to tolerate opera and chrome to the extent of sharing or swapping files. Does not firefox not behave itself when there is a younger one around? I suspect that it devourers its young for the sake of superiority. Yes or no to my last point, please.

I don't understand what you say.

Did you try what I told you?

You can try using vmware,where you can access two different os,so you can also use two different browsers.

A misunderstanding, perhaps. I did not want to run 2 firefox versions at the same time. What I have done is (and it seems to work for the moment):: Renamed /etc/firefox to /etc/firefox21. This I access via file manager>go>my computer>/etc/firefox21. Right click on firefox>properties>change premisions to anyone>close box. Click on firefox21 folder>box comes up>choose execute and it opens as firefox21. Close firefox21. I then download and install firefox24 via synaptic package manager and install it. Create a desktop symbol>click on it>firefox24 opens. This is the one I shall use the most. Note: If I try to open firefox24 via the shortcut on my desktop at the same time as having firefox21 open, I get another version of firefox21 open in a different window. IE I can run one OR the other and that suites me. Close question pl.

You will have to add the -no-remote command line switch to start the (second) version of Firefox that you only want to use occasionally.
The -no-remote switch hides the browser, so it can't be detected and you can't open an external link in a browser started this way, so do not use this switch to start the default browser or profile.
This switch works for starting the same Firefox version with a separate profile and for starting another Firefox version with its own profile.
Without this switch the startup code Firefox will detect that a Firefox instance is already open end will open a new window in that instance and you won't be able to start another Firefox version.

Many thanks for your help, one and all!