Everything anyone wanted to know about copyright is on the Internet. Copyright basics, a PDF provided by the United States Copyright Office, is a great place to start to get detailed information about what is and is not protected by copyright.
Anyone who creates is entitled to the benefits of their creative work. From the moment a designer saves the work to a hard drive, that work is automatically under copyright.
In general, anything that is the designer's original work is subject to copyright and anything that is not an original work or not in a tangible form (still an idea and not on paper yet) is not.
U.S. copyright laws do not require creator to register their work with the copyright office. However, depending on the work created registering a work records on public record who the work belongs to. If the designer is working on a global scale, registration also allows for protection against foreign copies from entering the United States for sale.
If the designer is posting his or her work on the Internet a copyright notice should be included on each piece of work or at the bottom of the Web site. By including a copyright notice it take out any questions about whether or not the work was intended for public use and can greatly decrease the amount of "idea piracy."
Copyright notices can be posted in a variety of formats. The important part is making sure the owner's name is somewhere easily accessible so there is no confusion as to who owns the copyright of the work.
Simply stating that a designer owns the work, does not always mean someone won't take an image and use it. Other methods include watermarking the image. Watermarks, in the context of images displayed on the Internet, is a faint image or text that overlays the main image displayed. Watermarks can be a company logo, the name of the owner or the copyright notice itself.
Watermarks are useful because no matter who gets their hands on the image, the watermark cannot be separated thus telling everyone who looks at it, that it belongs to someone else.