"Your faithfully" or the related "Your faithful servant" are formal closings from the 18 century and before. They are virtually never used today in the United States. If you are elsewhere, the custom might be different. "Yours sincerely" or "Sincerely yours" are common, relatively formal closings appropriate for most settings, except communications with good friends.
This is a matter of personal style and how well the sender knows the receiver. "Yours faithfully" is much more intimate than "yours sincerely", and should only be used with close friends and relations.