As between an Internet domain name registrant and a trademark owner, priority of rights lies with the trademark owner. Between two federally registered trademark owners, the senior mark has priority in disputes involving domain names. A mark comprised of an Internet domain name is registrable as a trademark or service mark only if it functions as an identifier of the source of goods or services. Because domain names generally indicate the type of entity using a given domain name, and therefore serve no source-indicating function, their addition to an otherwise unregistrable mark typically cannot render it registrable.