The Invitation: Solution
Written in a more intelligible font, the note reads:
Dear EastFlo Resident,
You ar cordilly invited to the etate of Mr. Boddy, esq. for a nigh o thriling puzzle slving Pleae arrive promply t 6pm on the eveing of riday, May 9th. Mr. Bddy has equeste that everyone (i.e tams an grops) leave 5/908 free to ommit severa hors to the festivitis. Look for more clues.
The missing letters, including the missing punctuation, spell out:
eastflo.stanford.edu/clue
which housed this more explanatory pdf.