His is it OK or wrong to have non christian friends (of the opposite sex) corresponding with online?
It's OK,but if your conscience tells you it's wrong then maybe it's wrong.
It depends on the motive. The person could potentially become converted, if that is your aim, then yes. If you do it just to flirt, then no.
It depends on your self because some are here to find a mate and may respond to you in that frame of thought.
It depends on whats your friendship about.