When you see the letter "C" enclosed in a circle, you're being informed the work is declaring copyright privileges. This symbol used to be required under U.S. law but today is not required. Works created before March 1, 1989, when the requirement was lifted, must continue to display the notice in the proper format--for example: ©1999 John Doe. Regardless, it's generally considered a good idea to display the notice because it informs the public that the work is protected by copyright. If the work is infringed on and the copyright mark appears on the work, no weight will be given to a defendant's argument that infringement was an innocent mistake.