Registered vs unregistered copyright depends on the country you are in and what year the story was written/posted. Most of the world has adapted the Berne Convention - see
http://en.wikipedia.org/wiki/Berne_Convention_for_the_Protection_of_Literary_and_Arti stic_Works for more info on that - and while the US restricts what can be sued for, it recogises that a copyright exists when a work is produced.
Before Berne... It was a mess, a real mess. If you have a few hours to kill, look up the mess about who owns the story Bambi and then there's the debate over if Mickey Mouse is in the public domain (if he was Steamboat Willy he is, otherwise things get complicated).
Now things are simpler. If it was written in Berne adopting country after Berne was adopted - there's a copyright.
Goodgulf