Changing the security settings in Firefox
When you install Firefox, two entries for Firefox are created under Programs in the Start Menu. One of these is called "Mozilla Firefox (Safe Mode)". Unfortunately, this entry does not truly make surfing safer, but only helps you find incompatibilities in themes and extensions by launching the browser with the standard theme and without extensions.
Unlike the Internet Explorer and Opera, Firefox cannot have separate security settings for different sites.
You can open the security settings with the menu option "Tools/Options":