What does this face mean :x ?
It's not a kiss if that's what you're thinking.
The animation sign denoted by": x" is used to express someone's lack of words or when one is speechless. They are commonly used in Skype and Gmail accounts.
Speechlessness like what joker .jeff said
Speechless, you don't know what you would say.
Speechless, or, My Lips Are Sealed