[Rexxar]

For example, native English speakers often make phonetic spelling errors (such as its/it’s, your/you’re) that non-native English speakers usually avoid. It’s probably a sign that someone speaks more fluently when he starts making these types of mistakes from time to time.

[Tade0]

Or picked up English before they learned to read and write properly.

I'm cursed with this as I was put in an international environment right before turning five, went back to my home country to start grade school and only in fifth grade started having English classes.