I have version 10.6.8 but need to use version 3.6 for bankreasons. Can i have both versions on my Mac or do I have to degrade?

Hey per.billing, There are a lot of benefits to running the latest version of Firefox. You might want to consider running the older version on [http://www.freesmug.org/portableapps on a USB Stick with PortableApps]. That way you'll still be able to run the latest version for your day to day activities. If you still want to roll back to a previous version of Firefox, just take a look at the Knowledge Base article [[Installing a previous version of Firefox]]. Hopefully this helps!