Comment 7 for bug 709125

The general.useragent.vendor* preferences weren't really supported, and have been dropped entirely as part of the UA string refactoring (see http://blog.mozilla.com/dwitte/2010/08/24/user-agent-string-changes-coming-in-firefox-4/). There is currently no mechanism for adding the vendor name.

The vendor details at the end of our UA string has also recently been a source of bugs where websites don't render correctly on Ubuntu, but do work correctly using upstream Mozilla builds.

I'm not sure of any way around this yet. "navigator.vendor" is also just a stub in Firefox 4, and returns an empty string if you query it with JS.