Internet dialect. It means "a dare
" it is commonly used if there is no way to (or you dont know how to) privately message someone and they just asked you why you are doing something humiliating
. If you unscramble the letters, it actually spells a dare.
internetdude1"dude2, why are you doing <insert humiliating act here>?"
internetdude2"d area" (or area d)
(note: chances are that people who you dont want to know will know what d area means. and then promptly yell it out for anyone who does not.)