Basically, "neh kid" when used, means no. No, in a sense that is similar to wow, epic fail, don't even try, and wow kid yur not kul!!
where i'm from, this term is used so often, that its presence has become annoying and when said is irrelevant and useless.
Kid#1: yo mamma's so ugly, her birth certificate was an apology letter from the condom factory!
Kid#2: Well yo mamma's so old... old... that shes older than you!!
Kid#1: Neh Kid.