Is content found on the Internet considered to be in the public domain and therefore not copyright-protected?
No. The legal concept of the public domain as it applies to copyright law should not be confused with the fact that a work may be publicly available, such as information found in books or periodicals, or on the Internet. The public domain comprises all those works that are either no longer protected by copyright or never were. Any content in a non-digital form that is protected by copyright will be protected in a digital form. For example, print books are protected by copyright as are electronic books. Analog musical recordings are protected by copyright as are digital musical recordings. A print letter is protected by copyright as is an e-mail letter (both generally owned by the author of that letter or e-mail). Web sites may be protected by copyright as a single work, and also the many different embedded works that are in that Web site may be individually protected by copyright.