CopyrightLaws have changed recently. In the past you had to file for a copyright in order to have it. In modern times, simply WRITING a piece of content gives you the copyright to that work. You don't have to file anything or even put a C on your content. You wrote it, you own it. Period.
Some people still put the copyright, name and date on their article as a "safety measure". Some people even add "all rights reserved" to the page which is another safety measure ensuring the document is fully covered in some foreign countries.
It is important to keep backups of your content. That way if you see a copy of your work on someone else's website, you can write them and insist they take it down. If they refuse, you can prove that your copy existed on your system long before they put their copy of it up. Their ISP is required to take down their work once you make the complaint - although the person can appeal. If they appeal and claim it really IS their work, now you have to take them to court to prove it.
If you decide to take someone to court, you can force them to take down the work if you prove it was stolen, and you can get damages of what they made from the work while they had it. If a website took your work and ran no ads, i.e. made no money, then you will not get anything.
On the other hand if you choose to go through the time and expense ($30 a submission) to copyright your work legally with the copyright office, and then someone steals it, you can now sue for monetary reward. You can get from $500 to $20,000 for your stolen work. But again, you have to pay the lawyer to do this work for you, and you have to sue someone who you can prove stole your work and has the ability to pay you that money. So this is a matter of choosing your battles wisely.
Steps for Filing a Website Copyright
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