How do you accept an invite to someone's mafia on mafia wars when they invite you through a message?

my friend sent me an invite in a message, and every time i click the thing that says join ___'s mafia, it just brings me to the main mafia page.
How do you accept an invite to someone's mafia on mafia wars when they invite you through a message?
Its a Prank someone is pulling your leg ,,Not such a thing as Mafia page..