It means to be suprised, like this ---> O.O <--- (eyes open wide)
Or to be looking at someone in a "one eyebrow up" kind of way like this ---> O.o <--- (It may be flipped to this ---> o.O <--- although It does means same thing) it's a way of saying "whaaat?" or "I don't know what you're talking about" or even "don't look at me, I don't know!"
Or it can mean "I'm confused and don't understand the current situation" like this ---> o.o <--- (eyes wide open but sort of small and hidden) this may be due to confusion or maybe simply trying to look cute.
Hope this helped...Everyone has their own opinion of what it means :D <---Happy face haha :D
o.o : blank stare, as in "You've just lost me" Or "I care about this...Why, again?"
O.o ; o.O : Confusion, usually used together.
O.O : Suprise, shock.
Person: (insert technical jargon here)
Person: and because of this, such evented happened, at such time, for such reason.
Person: You get it now?
Me: That was supposed to be helpful?
Person: (I'm blank on ideas, but anything that would suprise me)
Girl: *sobs* I broke up with Tony!
Friend: Oh, my gosh! What happened?
Girl: I found him kissing another guy!
Friend: o.O... O.o
Boy: I heard that they're going to take all the good channels off the air like the movie channels and such.