Do 'you know'? it is an expression, not a question, "you know !" without the "do" in front, this expression havn't any meaning. We don't use it in writting. So, there is no " y know". In oral conversation, "you know !" it assume that you should know without my words. (The less educated people used this expression more often. But, it is not an offensive language)

This is what we call a verbal pause. It is quite common, but does sound very informal. We would not want to overuse something like "you know" in a formal situation, such as an interview or a toast. Other verbal pauses, which people just "add in": "sort of" "like" "um" / "uh" "well" "so ... " Sometimes, "you know?" can be added as a way of being sure the other person gives feedback to corroborate information: Ex.: "Do you remember the name of the film we watched in Sociology last year -- the documentary about child soldiers in Africa, you know?" This is inviting the other person to add more detail, to be sure you are both thinking of the same thing.

Hello Romulus, It is a rhetorical informal question and it doesn't refer to poor English! It is mostly used in small talks and daily conversations to confirm the other knows already what is being said. It is a friendly approach to keep the listener hooked up to the conversation.It is almost like saying : " Of course you know!" " I know you are aware of what I am talking about" "We are probably sharing the same thoughts or opinions"

@rumulos i feel weird about your question.hummm your punning the word "do 'you know'? " am i right on that? cowboy...

"a sign of poor english" (c) you