I used to believe that the UL symbol on boxes of lightbulbs meant that they were kosher. I obviously had no idea what kosher meant, and the UL must have looked a bit too much like the "circle U" symbol I'd seen on other items in the grocery store.
A childhood belief about general

others believed things like this
- I used to believe that rounding a number meant drawing a circle around it.Anon
- I used to think being engaged meant being in jail. I have no idea how I came to that conclusion.— CNB
- I used to believe making a cake from scratch meant using a box mix rather than buying a cake from the store.— EZ
- i used to believe that sex meant love and that having sex meant the two people would live happily ever after.— amy
- I used to believe that take a shower meant to go steal a shower from the storeAnon
- I used to think "public convenience" meant a convenience store!Anon