"Ne ayaksin lan sen?" is a slang idiom. Literally translated it means "What foot are you?" The word 'lan' is not included in the literal translation as there is no English word for it. "Lan" is an interjection of address, used only informally and considered very impolite when said to strangers or persons older than oneself. Example of an interjection of address in English "man": "How are you, man?" 'Lan' doesn't mean 'man', it's just also an interjection like 'man', constituting 'you' but informal and impolite. The correct meaning of the idiom is: "What are *you* all about?" "you" being emphasized. Use it just as you would "what are *you* all about". But bear in mind, it's slang, informal speech and you're *always* better off never ever using the word 'lan', so just "Ne ayaksin sen?". If this remains unclear i can add examples, just ask. Regards. Sertan.

in additon to the explanation of @Sertan, i can say that it means "what kind of person are you" OR "what kind of *business* are you after" , "what are you trying to do"

It's kind of slang. Ne: what, ayak: foot, -sın: you are, lan is like "the hell" (For example "What the hell did you do?") but it doesn't always express anger, we use it while talking to a friend too. "Lan" is sort of hard to explain. Ne ayaksın lan sen? is not equal to what damn foot are you? of course. That wouldn't make sense. Ne ayaksın lan sen can't be translated to English, but I can say that it has the meaning of "What the hell are you trying to do?".

Hi. You can add me via skype id that is "bosstanci". I m native Turkish speaker.. Thx :)

:)