Yes, I'm getting 404's there too -- I guess the original author (it was user contributed) must have removed the file from his/her Dropbox account.
Sorry, no manual, but there is an FAQ and a forum (this forum here).
A lot of things come up over and over again, so if you have a question, both the FAQ and searching the forum (top right) can help. If not, feel free to post your question(s) here or email support <at> aqua-mail <dot com>.