I see a paradox:
Because the notebook has a finite number of pages, and you would have to have an infinite number of notes, you would eventually run out of pages.
This would cause the note to cease to exist.
Because the note doesn’t exist, the notebook doesn’t run out of pages, so the note does exist, so it doesn’t exist etc.
Confusing, isn’t it?

Hmm, the way I see it, when the note goes back, it will go back to a point before the page has been taken out the notepad, so that it is the same page that will be continually taken out time and time again. If that makes sense?

Excuse me while I shake my brains out for a few minutes.

Interesting twist on the warning from the future.

Wait, what is this about infinite loops? Are you assuming that the character would warn himself about the warning?

Yes, the notion I had was that the contents of the note are concerning the note itself.

My mind does get a bit twisted like that sometimes :s

@ i, Coomber:
But, the note would still have to be torn out of the notebook to make it.
So it would run out of pages, yadda yadda yadda.

@The Note Writer, this would be easier with diagrams, but I hope this helps.
1. Man recieves note from future, the page is printed as page 1. His current notebook is untouched.
2. Man gets notebook and writes note on page 1.
3. The note he has written (somehow) goes back in time. The note he recieved stays with him.
4. The event is behind him, Pages 2 onwards remain untouched, man puts notebook away and carries on with life.

Mind-bending, as time travel tends to be, but amusingly told in this case.

You are all wrong. The notebook would collapse in on itself and all of the world would be spaghettified.

Hmmm, spaghettified you say, possible sequel idea in there somewhere???

Time travel does play hell with the verb tenses, as Douglas Adams would say! Bravo, I love time travel.