You can see which dictionary is selected if you right-click in a text area and open the Languages submenu. At least one dictionary should be installed and have a check mark to indicate that it is selected.

• Open the "Add Dictionaries" link to install a dictionary if you do not have one.
• Make sure that [X] "Check Spelling" in the right-click context menu is check-marked.

You can enable or disable spell checking globally:

• Tools > Options > Advanced : General: Browsing: "Check my spelling as I type"

You can look here for dictionaries:

• https://addons.mozilla.org/firefox/language-tools/

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Thanks but has made no difference what so ever. I have installed English Dictionary and spell check.

In what way is the spell checker not working?

Are all words underlined or none?

What is the value of the spellchecker.dictionary pref on the about:config page?

• spellchecker.dictionary
• layout.spellcheckDefault
• ui.SpellCheckerUnderline
• ui.SpellCheckerUnderlineStyle

Its working now :D I had to uninstall Firefox. I had the English (UK) edition. Now I have the US version and it works. But still puzzled why the UK version wouldn't spell check.

The UK version doesn't come with a spell checking dictionary and this dictionary needs to be installed separately.

• https://addons.mozilla.org/firefox/language-tools/

Only the en-US and maybe fr and maybe a couple others of Thunderbird and Firefox come with a dictionary due to licensing reasons.

That is what I had done before. Ill leave it with the US version. Thanks for your help :)