Change one letter. Delete one letter. Add one letter. Someday, perhaps ispell will be extended so that words that sound alike would also be considered near misses. If you don't want near misses, instruct to produce only a list of unknown words.
Statistics Do some basic statistics on input file.
Statistics is based on English character set. If something internally goes wrong, select this option. Only if checkbox is selected, a mail containing unknown words is send to specified e-mail address. WWW browser can report the name of your machine, but you must define valid username of e-mail recipient. You are advised to use this possibility, if the document to be checked is too big and your browser can not wait for the process to be finished.