You may have noticed, I write can not as two separate words, not as the more common cannot. There is a reason.
When I was a Junior in high school, I wrote a paper in English. I spelled can not as two separate words. It was marked as incorrect.
I informed my teacher, Mrs. Anderson, of her error. (Politely, of course.) Mrs. Anderson informed ME that can not is written as one word.
I then (politely, of course) used the dictionary in my desk to prove that either spelling is accepted.
Mrs. Anderson said that she would mark it as correct that one time, but in the future I was to write can not as ONE WORD.
I asked Mrs. Anderson (politely, of course) why Daniel Webster's spelling wasn't good enough for her. Mrs. Anderson threatened me (none too politely) with detention. I spent the remainder of that semester avoiding the use of the phrase can not in order to elude her decree.
Furthermore, I have never since spelled can not as one word.I can not think of a better way to demonstrate my utter disgust at her petty display of power.
(That is, and still be polite. Of course.)