I have screwed up a number of times and have added words the dictionary that I wanted to correct the spelling of. Is there anyway to make sure this misspelled word doesn’t show up as a word any longer? Yes, you can edit your corrections to the dictionary. Just look here:
Documents and Settings\Application Data\Mozilla\Firefox\Profiles\.default\
Now find the file called “persdict.dat”. Open that up in a text editor, delete the words you don’t want in there, and then restart Firefox. You should be good to go.