Its easy to be Wrong

Robin did use "Quality" as one of the four C's of diamond buying.

However, Robin did not say "cut, clarity, carat and quality". (*)

Robin's mistake was " cut, clarity, color and quality".

This is getting Silly, the website's mistake is far more egregious then Robins mistake.

(* RobinsWrong.com post was updated with Robin's actual mistake.)