Įven if the uninstall fails, as it may in some cases, continue on with the rest of the uninstall instructions. This option has been removed in Firefox 31 so, if you wish to remove your Firefox user profile data, you will need to do it manually ( see below for instructions). DO NOT select this option if you want to keep your Firefox profile data and settings. This removes your Firefox user profile data (bookmarks, passwords, cookies, extensions, preferences, etc.). Note: In Firefox 30.0 and below, the uninstaller includes the option, 'Remove my Firefox personal data and customizations'. On Windows XP (or below), double-click 'Add or Remove Programs' Select 'Mozilla Firefox ' in the list of installed programs and click 'Remove' to run the uninstaller.On Windows Vista and above, go to 'Programs -> Programs and Features', select Mozilla Firefox and click click Uninstall.Exit Firefox completely, open the Windows Control Panel and then, The first thing you should try is to make sure that you have the latest Java.

Java security settings are set too high.

You are using outdated Java (below Oracle's security baseline).

If a web page with Java Uploader or Downloader displays correctly, but does not upload or download chosen files, this may mean two things:

If you click the Allow now button, you will encounter this problem again when visiting other web pages that use Java. When you click Allow and Remember Firefox adds the current webpage to an internal whitelist, whereby the Java applet will run automatically in the future without further intervention.

Firefox os x