So...interesting little tidbit of information I came across here...
We've all heard of Murphy's Law (Anything that can go wrong, will go wrong); but have you ever heard of MUPHRY'S Law!?
Muphry's Law states that "if you write anything criticizing editing or proofreading, there will be a fault of some kind in what you have written." (Thank you, Wikipedia!) Here are the four parts to it:
(a) if you write anything criticizing editing or proofreading, there will be a fault of some kind in what you have written;
(b) if an author thanks you in a book for your editing or proofreading, there will be mistakes in the book;
(c) the stronger the sentiment expressed in (a) and (b), the greater the fault;
(d) any book devoted to editing or style will be internally inconsistent.
Basically, if a mistake is as plain as the nose on your face, everyone can see it but you. Unless, of course, you look at it cross-eyed, but no one really does that for long, do they?