What is Yeah, No?
1.
Yes, to gain the attention of the listener and then no to answer their question...
Don't you think I'm cool?
Yeah, No!
2.
An affirmation of understanding what the speaker of an inferred phrase or question means but, also answering that the particular phrase or question is not ok or inline with your way of thinking. Can also be used in a derogatory sense to give a false sense of understanding to the speaker.
Do you remember that dance that Elaine did at the office party? Yeah, no.
See
3.
When you agree on something, but not completely.
Them: I think that we should go that way, and get some KFC.
You: Yeah, no lets go that way, then eat some Subway.
See