Hi, english-en is the USA Dictionary and if you are using that with a different version local browser you need to add the appropriate dictionary. Which you can check if you have more than 1 installed so you can disable english-en go to 3 Bar Menu --> Add-ons --> Dictionaries. So if more than 2 disable english-en. Go to here to find your right dictionary https://addons.mozilla.org/firefox/language-tools/ and install it.

Please go to the 3 Bar Menu --> Options --> Language and the box that shows Choose please Click it. If you have more than 1 Language listed there please choose the correct one.

Please let us know if this solved your issue or if need further assistance.

The dictionary is now set to english-gb and the others deleted.The spelling used seems to be American. e.g. Labour brings an error .Only eliminated if the spelling is changed to Labor.

Does that editor use the builtin Firefox spelling dictionary since it is possible that this editor comes with its own spell check feature?

Do you have the Language menu if you right-click in the editor to select the dictionary?

My facebook is set to use english (uk) for use in facebook.There doesnt appear to be any other settings for language.Also this problem doesnt occur in either Chrome or Opera both of them i use in preference to Firefox.

You should use the Browser that matches the Language region your using. There is a UK FF version also Chrome will auto language change of which FF can't do when reading different language site.

What eventually sorted it out was either installing the eng-gb dictionary.Or doing a refresh FireFox from the download page which automatically installed ENG-gb.