Some older versions of firefox are available, another alternative may be to change the user ID string, but newer versions of firefox tend to be more secure. Are you certain you are accessing the correct site.

Are you currently using internet banking with this bank ? if so which browser are you using, and have you been doing this trouble free for a number of months ? (Long enough to be sure transactions are processed correctly)

Maybe if you state your country and the name of the bank someone will be able to give a more useful reply.

PS

Sorry I did not initially read the Sytem Details etc that you have already provided. The site looks genuine and does say firefox 3.0 is supported. There is probably a good possibility it also supports firefox 3.6.13, the bank does give email contact information, why not email them and ask them to confirm the latest version of firefox v3.6 is supported.

What problems or error messages are you getting ?

• see Enable SSL to fix the Firefox cannot connect securely error message

If you really need the older version then install a portable 3.0.x version.

See:

• http://portableapps.com/apps/internet/browsers/portable_firefox
• Firefox 3.0.x: http://portableapps.com/apps/internet/firefox_portable/localization#legacy