When I was four or five and just starting to read I was very confused by the small print on packets of toilet paper. I read "2-ply" and thought this was actually a list of instructions, of which point 2 was "play". The fact that the "instructions" didn't say what you should play with, and that there was no number 1 (as it were) in the "list", didn't stop me from holding this belief for some time, to the frustration of my Dad who attempted several times without success to explain to me what "ply" meant.
A childhood belief about reading

others believed things like this
- I used to believe that the credits at the end of a movie was a list of people in that were watching it.— jon_
- when my friend was little, she used to eat paper, thinking it would make her read better.— hehehe
- As a kid, I thought "No Outlet" signs meant the houses past that point didn't have any electrical outlets.— Julie
- After my dad read The Hobbit to us, when we were little, I thought that Gollum lived in the toilet. — PixelFish
- I thought that toilet paper was bread and by puting it it the toilet i was feeding the ducks at the bottem.— Gringo
- For the longest time I was sure my cat could read my mind.Anon