Firefox has a really useful built-in dictionary that underlines a misspelled word, so you can see at a glance whenever you have typed something wrong.

But you might have noticed that when you type a wrong word into the email subject (in Gmail for example) or any single line element, it doesn’t work.
Yes, the default setting corrects and spell checks all multiple lines areas, leaving it to you to find errors in single lines box such as titles, subjects, tags…
Here are some quick steps to set Firefox to check every field:
- Type about:config in the address bar and look for ‘layout.spellcheckDefault’.
- The default value is 1, which means that Firefox will spell check all “textarea” fields, but changing it to 2 will make it check all fields of any kind.
You can also deactivate the spell checker function by setting the value to 0, but I suggest you keep this function on as it doesn’t really bother, but can really help you out with distraction errors and mistakes.

how do you force the spell checker for places like gmail?
It already works in Gmail by default.
Plus, by changing this value, it also makes it check the subject box…does it not for you?
While I change the FF3 speller from 1 to 2 it will not check all field and forms that I must fill in. Is there something I am overlooking?
When typing email on hotmail, the spell checker isn’t working. I have gone into tools-advance, and the box is ticked next to check spelling. Have also changed value to 2 in aboutconf, restarted computer, but still not checking.
Any suggestions please?
Thank you, this is priceless for me – my spelling is atrocious!
@Irene Duffin, if nothing would help, try this one free online online spell checker:
http://www.spellchecker.net/spellcheck/