Firefox automatically checks the spelling of words that you enter in text boxes containing more than one line. As soon as you finish typing a word, it is checked against the words in the installed dictionary. If the word is not found in the dictionary, it will be underlined in red, as in the following example:
By default, Firefox is configured to automatically check spelling. You can turn it off in the OptionsPreferences window:
When spell-checking is enabled, you can easily correct misspelled words. To correct the misspelled word, Right-clickHold down the Ctrl key while you click on it and select one of the suggested words at the top of the menu.
If none of the suggested words is appropriate, you must manually edit it. If you are sure the word is spelled correctly, you can add it to the dictionary. To add a word to the dictionary, Right-clickHold down the Ctrl key while you click on it, and select Add to Dictionary.
You can install other dictionaries as necessary.
After the dictionary is installed, you can switch to it, as needed. To switch to a different installed dictionary, Right-clickHold down the Ctrl key while you click in a multi-line field, select Languages, then select the dictionary you want to use.
Open your profile folder:
Click the menu button , click help and select Troubleshooting Information. The Troubleshooting Information tab will open.