In Firefox you can edit or remove the misspelled words, this way edits your persdict.dat file. This will works on Windows 7 mainly, follow the simple steps below
Locate your persdict.dat file. The easiest way to do this is as follows
Another, quicker way:
Once it has been found, open it. Your computer may not know what to open it with. Select the WordPad program to edit it with.
In WordPad, start going through your list of words. Look closely. Some of the words will be pretty easy to miss
Don’t be surprised to see some odd characters in the file. Those are accents and such that are added to words
Select and delete the misspelled words. Look over it a couple of times, or better yet, have someone else look it over.
Save your file. Press CTRL S (or click on the floppy in the upper left corner) to save
Restart FireFox. The misspelled words should now have been removed.