Some websites or add-ons require that you use a specific browser or version and then make a mistake detecting your installed version of Firefox. This can cause the following problems:
If the website or add-on is compatible with your installed version of Firefox, the cause of the problem may be in your Firefox "User Agent" string, that identifies your browser type to websites. You can remedy this problem by resetting your user agent in your Firefox preference settings.
To reset your user agent:
In the address bar, type about:config and press EnterReturn.
After resetting your user agent, you may need to clear your cookies and cache:
If resetting the above preferences does not work, see:
Some websites incorrectly see the latest version of Firefox as version 1 (instead of version 10 or above) and will think that Firefox is outdated, incompatible, or not supported. We are working with websites to get them to fix this. In the meantime, you may just be able to ignore the message but you should report the problem website:
Occasionally you may come across a page that simply doesn't work in Firefox. If that happens, please report the problem to Mozilla as follows:
You may be able to restore functionality by temporarily disguising Firefox as another browser. To do that, you can install the User Agent Switcher extension:
When Firefox restarts, you can disguise your Firefox user agent so that websites think you are using Firefox 9.0.1, as follows: