The creation of Firefox-profiles is quite easy.
Windows-XP: ‘Start-button’ -> ‘Run’ and type
Mac OS X: Open the ‘Terminal’ and type
This will bring up the Firefox Profile Manager where you can create, rename and delete profiles for Firefox.
So you’ll see the default-profile in the Profile Manager. Create a second profile (e.g. for web development) and remember the exact name of the profile. After creating the profile, press ‘Exit’ in the Profile Manager.
Now, there are different possibilities to use two independet Firefox instances using different profiles simultaneously. You could write a batch-file that includes parameters or you could start Firefox with parameters set in a shortcut.
I prefer the method of using Firefox-shortcuts with parameters. The magic parameter is called ‘MOZ_NO_REMOTE’ and has to be set with some other options. So right-click anywhere on your desktop/folder and click ‘New -> Shortcut’. The line of your shortcut has to be as the following:
So if you have created a second profile called ‘development’, your line has to be like this:
That’s it. Just create two shortcuts with the corresponding profile-names in order to use two profiles simultaneously.