Hating YouTube Location Suggestion bar? Great! (0:
Copy following content in a .CSS and place it in Mozilla Firefox runtime directory(https://developer.mozilla.org/en/Runtime_Directories) in Windows. Start run--> %APPDATA%\Mozilla\Firefox\Profiles\xxxxxxxx.default\ and press enter to open the folder.
@-moz-document domain(youtube.com) {
div#default-language-box {display:none !important}
}
Restart the browser, and enjoy!