Edit Mispelled Words in Firefox

Firefox keeps a per profile dictionary of custom words. To correct words which inadvertently enter it: 
 
 Go to “% APPDATA %\Mozilla\Firefox\Profiles” 	 On Mac OS X, go to “~/Library/Application Support/Firefox/Profiles” 	 Enter the profile folder, usually like “.default” 	 Edit “persdict.dat” with a text editor (WordPad, Notepad, or Textedit) 
 
 Save, and done.