hello Zenagp, your useragent (the information the browser sends to websites to identify its version) - apparently mistakenly - shows you're on firefox version 3.6. probably some sort of toolbar or adware has overwritten it. please refer to this article in order to reset the user-agent settings in firefox: How to reset the default user agent on Firefox

Hello Zenagp and philipp,

Zenagp note also that you you cannot go beyond Firefox 3.6.28 (today latest stable version is 31.0), for your Mac OS X 10.4, see:Firefox no longer works with Mac OS X 10.4 or PowerPC processors.

thank you

What Mac OS version do you currently run?

The FBSMTWB in the user agent is caused by a Fast Browser Search infection in the past that likely locked the user agent at that time and is likely caused by the general.useragent.override pref that you can inspect and modify on the about:config page.

As of Firefox 4.0 you needed Intel and OSX 10.5+ up until Firefox 16.0.2. https://www.mozilla.org/en-US/firefox/4.0/system-requirements/

The minimum since Firefox 17.0 has been Mac OSX 10.6+ /firefox/17.0/system-requirements/ https://www.mozilla.org/en-US/firefox/17.0/system-requirements/