If you're going to be publishing content on the Internet it is imperative that you understand copyrights, both so that you know what you can use, and so that you know when your own rights have been infringed upon. I am not a lawyer so I cannot offer you legal advice, so the following information on copyrights is solely for educational purposes. If you need help on a specific issue you should contact an attorney. Also the information presented is from a U.S. standpoint, if you hail from elsewhere I suggest you lookup the laws in your country.
A copyright is a legal protection given to the author of a work. Having the copyright to something gives the holder the right to reproduce the work, make derivative works, distribute copies of the work, perform the work, or display the work. If you do not own the copyright to something you cannot do any of the above. It doesn't matter if you profit off it or not, it doesn't matter if you're using it for education or anything else, it doesn't matter if you put a disclaimer that its not your work, you cannot do it.
A work does not need a copyright statement to be copyrighted either. Any original creative work that has a fixed form has been automatically copyrighted upon its creation since 1976. Does this mean that everything is copyrighted? No, only those original creative works with a fixed form. No one can copyright the idea of a left menu or rounded table corners, they're not original enough. Now I know some of you who run dynamic sites may be apprehensive about that fixed form requirement so let me explain that. What having a fixed form means is that even if the ideas expressed within a document are not unique the formatting of that document is copyrightable. For instance if you created a flier with the Gettysburg Address on it you could still copyright the formatting and presentation of the address if not the actual address itself.
Coming back to copyright statements. While they are not required for a work to be copyrighted they are often a good idea. Not everyone knows about copyrights so placing a statement on your website would deter those who steal out of ignorance. Additionally if you have to go to court over a copyright issue that there was a statement present could result in increased damages rewarded to you as the culprit cannot claim ignorance as their defense.
When constructing a copyright statement you should use the following format:
Entity © Year Name. All Rights Reserved.The copyright symbol is important. You should not substitute it with (c) as only the copyright symbol has ever been given legal power. Additionally the phrase "All Rights Reserved" used to be required, and may still be in some countries, so it doesn't hurt to add it.