I have firefox 7 and still get warnings "You are using an old version of Firefox which Gmail no longer supports or Google Plus incompatible. How can I fix?
When I tried to join Google Plus I get the message Browser no longer supported. First Happened when using firefox 6.0.2 and still happens now with FF 7. Also Gmail shows "You are using an old version of Firefox which Gmail no longer supports. Some features may not work correctly" and at the bottom of this page the "educated guess" about my browser shows 3.0.15
Opaite Mbohovái (1)
Your about:config has been modified with the lines
general.useragent.extra.microsoftdotnet
( .NET CLR 3.5.30729) general.useragent.override Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15; .NET CLR 2.0.50727; ffco7) Gecko/2009101601 Firefox/3.0.15 …
That is why Google is reporting old version.
You need to ether find out why or create a new profiles and see if this line is gone. Profiles - Where Firefox stores your bookmarks, passwords and other user data There is some verbose about MS, but I don't know of any MS add-on that would do this.