I have some javascript on domain A which would load a file on domain B, and I need to enable cross site data transferring in browsers. For IE, I can set it in Options -> Security -> Custom Level -> Enable Cross Site Data transferring For Chrome and Safari, launch the browser with additional parameter --disable-security-server But for firefox, I don't know how to do this, when I am visiting the web page on domain A, it returned me 401 unauthorized error.