I am assuming you are using an iphone - this is an exerpt from apple help
To prevent users from maliciously redirecting phone calls or changing the behavior of a phone or account, the Phone application supports most, but not all, of the special characters in the tel scheme. Specifically, if a URL contains the * or # characters, the Phone application does not attempt to dial the corresponding phone number.
They relaxed it on the *
but not on the hash - it is annoying I know!