It is illegal for anyone to violate any of the rights provided by the copyright law to the owner of copyright. These rights, however, are not unlimited in scope. Sections 107 through 121 of the 1976 Copyright Act establish limitations on these rights. In some cases, these limitations are specified exemptions from copyright liability. One major limitation is the doctrine of “fair use,” which is given a statutory basis in section 107 of the 1976 Copyright Act. In other instances, the limitation takes the form of a “compulsory license” under which certain limited uses of copyrighted works are permitted upon payment of specified royalties and compliance with statutory conditions. For further information about the limitations of any of these rights, consult the copyright law or write to the Copyright Office.
http://www.copyright.gov/circs/circ1.html
Example found on this site :
Why does it say Copyright © 1998-2003 WhatisCopyright.org at the bottom this webpage? Those are the dates that I created and/or modified the layout, text, graphics and other material displayed on this web site and saved it to my hard drive. That entitles me to claim copyright. Only I, as the author and creator of this work, am entitled to use, reproduce and distribute this material unless someone else who wishes to use it obtains my prior written permission to use it as well, and only in the manner that I previously approve. What does this mean? That nobody may access my web site and copy my layout, text or graphics until I provide a written document that states, “Yes, you can use my work, but only in the manner that I deem appropriate.” This especially goes for those who want to use my material for lucrative purposes.
Would you let someone sell letters you’ve written for publication in a magazine without your permission, and particularly without getting some of the profit? Anybody who uses, copies or distributes my material in any manner, for commercial or personal purposes, without my written permission, would be committing an infringement of my copyright. If I, at any moment, detect a violation of my copyright by another individual or entity, I am entitled to assert a claim. It doesn’t matter if you are a “newbie” or if you “don’t know any better”. As a principle of law states: “Ignorance of the Law does not make one exempt from compliance thereof.”