Restricting passwords is a no-no!
It's this simple. Please don't enforce maximum length passwords, or specific characters in passwords. I like my random 14 character password. It's 14 characters for a reason, and it's random for a reason. I hate being told you have to simplify your password and absolutely no justification as to why
I have to lower my security standards so it can work with someone else's website. I agree passwords should have a minimum length of 6-8 characters (generally), however restricting the maximum is like punishing you for trying to do the right thing and having a decent password.
People who do this should at least have the "minerals" to explain why they are enforcing such a stupid policy.
Of course if you still continue to enforce this practise I'll be forced to eat your babies!