* To change the language of the Firefox user interface, run the setup file for the desired language. ** https://www.mozilla.org/firefox/all/ * To change the list of preferred languages that you send to websites, see ** [[Settings for fonts, languages, and pop-ups]] * Some sites will display pages in a particular language based on your IP address, ignoring the aforementioned list of preferred languages. Check the preferences on the site itself for a way to change this, e.g. ** https://support.google.com/websearch/answer/873?hl=en ---- It looks like your system may be infested with malware. You have the [http://malwaretips.com/threads/toolbar-widdit-a.31228/ known malware Widdit plug-in] installed, and your user agent string has been tampered with. Perform a full system scan with following tools, and reset your user agent string. * [[Troubleshoot Firefox issues caused by malware]] * [[Websites say that Firefox is outdated or incompatible even though it's the latest version|How to reset Firefox's user agent string]]