Short Copyright Facts
The owner of a copyright has the exclusive right:
* to copy the work
* to modify the work
* to distribute the work
* to perform the work publicly
* to display the work publicly
Copyright is important when you obtain content for your site, and in the protection of your content. Copyrightable works are usually on the form of text, image, music, etc. Facts, titles, recipes, form designs, alphabetical lists and other items do not have the required "originality" to merit copyright protection.
One of the misconceptions about copyright protection is that you have to register your work to gain legal protection. If you do protect your original works, you are more likely to win attorneys' fees and, sometimes, higher damages.
The term "Public Domain" does not mean that everything in public or on the Internet is free from copyright protection. It refers to items that either do not qualify for copyright protection, or for which the protection has expired. The default you should assume for other people's works is that they are copyrighted and may not be copied unless you know otherwise.
The correct form for a notice on your web site is:
"Copyright [dates] by [author/owner]"
You can use C in a circle © instead of "Copyright" but "(C)" has never been given legal force. The phrase "All Rights Reserved" used to be required in some nations but is now not legally needed most places.
Even if you don't charge anyone for a product that contains copyrighted materials, you are still violating the law. An example of such an unlawful act would be when Napster enabled widescale download of copyrighted music.
One exception would be fair use. Copyright law does not block your freedom to express your own works. For example, you may be reviewing an article from a news paper's web site that requires you to reproduce some of the work on your site is not the same as simply copying the work to your site so you don't have to create your own work. Of course, that does not mean that you can start posting articles from other web sites and pretend you are reviewing them, but you are simply stealing content to cut corners.
One of the key to the fair use doctrine is that you can not diminish the value of the original work. Copying just 300 words from Gerald Ford's 200,000 word memoir for a magazine article was ruled as not fair use, in spite of it being very newsworthy, because it was the most important 300 words - why he pardoned Nixon.