I like finding that people who write code have a sense of humour:
This lets you specify which characters are permitted within your URLs. When someone tries to submit a URL with disallowed characters they will get a warning message.
As a security measure you are STRONGLY encouraged to restrict URLs to as few characters as possible. By default only these are allowed: a-z 0–9~%.:_-
Leave blank to allow all characters — but only if you are insane.
Well, it made me laugh.