Copyrights don't need to be registered. Anybody who charges you to register a copyright for something, is taking your money for no reason.
Everything and anything is implicitly copyrighted automatically, from the moment it was created. This almost certainly includes dynamic content (unless someone else has prior copyright on some of the content).
There are obviously a lot of grey areas - especially content syndication (e.g. by Google) - but as far as I'm concerned, publishing media in a format which allows content syndication is pretty much inviting people to do so.
As long as they don't claim copyright (and respect all other restrictions) over your content, then it's fine.
Tricky with, for example Google, who collect information automatically without a human reading the copyright statement on the site. You can of course, forbid Google to do so, and they will respect your request.
Mark