I know what you're thinking, and no, it is not that. There is white stuff on the edges of certain keys on my Macbook Pro that appear at random. It is like white and slightly hairy like dust. My best guess is that it is dust floating in the air mixing with the sweat from my fingers on the keyboard and sticking there. It appears on the edges and inward from the tops of keys. I can't describe it other than that it's white stuff. What is it?