It means something along the lines of, "you're a little bit dumb" or "you're a little bit stupid." Atama warui = stupid. It doesn't mean weird, crazy, or perverted. There are other words we'd use for those: atama okashii, kawatteru, kurutteru, sukebe, etc.Cereth said:"anata no atama wa sukoshi warui desu ne"
" your head is alittle bit sick"
it is a phrase that means you are not ok of your mind...maybe because you are weird, crazy or even pervert.... (well but not so much..just a little bit)..