Hello A working environment (user) in a given situation does not correspond to a working environment (other user) in a given situation, please understand that it is difficult to give an opinion, in the absence of the relevant page. Website will not allow Firefox to display the page if another site has embedded it. https://support.mozilla.org/en-US/kb/xframe-neterror-page If you wish to test, Ignore X-Frame-Options Header. https://addons.mozilla.org/firefox/addon/ignore-x-frame-options-header For demonstration purposes. https://www.youtube.com/watch?v=EQVDFcBKJTM