As mentioned above, copyrights are the rights of an owner to something. Even a sentence copied without permission can be termed as copyright violation. This is probably one of the things that the recording and movie entertainment organizations are facing; with the ability to not only get access to and download music and movies, there has been a real cry from artists about the 'freeness' of getting 
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their works.
How does someone become aware of a copyright violation? Companies are able to either stumble and find something of theirs that is being viewed or used (such as on YouTube) and the same can be said for anyone who stumbles around the Internet and discovers that their book, their song, or their design is being used by someone else without permission.
In the case of online content, the waters are a bit murky, but there are points to know and understand.
- Design and content of a website are two different things. The writer may own the text, but not the design (including logo, images, etc) of the website.
- The design belongs to the designer, who is also protected by copyright laws.
- The writer will have rights only to the content of the site unless the design rights have also been transferred under valid written agreements or the writer of the site is also its designer.
In the United States, any article written by an author becomes their property and they own the full copyright upon finishing the creation of the article with their name attached to it (unless the author has an agreement to release the rights to another person or entity). However, in order to have full legal protection and backing, a record of this must be on file with the United States Copyright, Patent and Trademark Office. Unfortunately, the costs of legal action far outweigh the result of it, and many freelance and independent writers cannot afford this risk.