Why would a guy stare at a girl with his mouth slightly open?

[Anonymous]

Soo what does it mean if a guy stares at a girl with his mouth slightly open, and a little smile on his face?
This happened a week ago while I was in college. I don't really know the guy, but I caught him staring like that. Also I've caught him glancing at me here and then.
But what the staring with his mouth slightly open, and a little smile on his face could possibly mean?

[pharaoh_lover48118]

that means he is daydreaming.. and I won't do so unless I find this girl extremely beautiful , hot or both.

[SpeakNoEvil]

He likes you.