At a certain point in the movie Paranormal Activity, the entity writes a message out on a Ouija board. However, I was unable to make out what it said, if anything. It seems this was the only time when the entity tried to convey a message to the family. What did the entity write out? Was it an actual message or was it just gibberish?
It appears the answer is that it is never clearly explained in the movie (and perhaps in the sequels).
Below comment from @Walt explains it -
They show the board up-close and there are some vague scorch marks on it, but nothing readable. He just comes to the conclusion that it spell out 'Diane' (which leads him to the website about the possessed girl), but we don't know if he's right. We just assume it.