"How many websites have you seen that only support letters and numbers for passwords? Too many in my book." Very true, though this is generally to prevent XSS or SQL injections. If you didn't allow the keys ' " = < and > then you're potentially confusing users with what they can and cant have in their passwords, thus why some sites only allow alpha-numeric passwords As for first work from a song or mnemonics, I quite like the idea and may start using them! Very interesting post!