I am planning for a website startup, in which i use the data added by the people which is accessible to every other user. Now i want to make sure that the data that has been entered by a particular user, though it can be accessed by everyone, but i dont want anyone to claim for that particular data. I want to make sure that the basic rights of that paricular data belong to the one who uploaded it. How do i do it? Is it something to do with the copyrights, if yes then what? else what to do?
Everything you have in the internet can somehow be stolen: videos can be captured, text typed or copied, images screenshot.
If you are speaking of videos or images, you could try to make some kind of watermarks, like you can see on http://www.istockphoto.com/ But it is ugly, because visible.
In case of text, you really can't protect it. If you can read it, you can write it, in worst case.
You will have to add copyright notices on your webpage. Of course this does not protect you before abuse. You can just make sure your user can claim their rights, if necessary. In this case I would recommend you to visit a lawyer.
Problem is, if you live in the US and have good copyright text on your page for the US, the law might be different in different countries. After all somebody from Hula-Bula Islands somewhere between India and Africa probably does not care about that at all. To make sure people are going conform with the US law, you probably need to restrict you user base to countries of which laws your are familiar with.
You also might want to allow upload only if your users choose a "Creative Commons" license. http://www.creativecommons.org/learn/licenses/
So, now it depends on what data you want to protect and how sensitive it is.
Unless your users are specifically giving up their copyright when they upload stuff to your site then their basic rights are automatic.
As soon as you have created an original piece of content you are the copyright owner (in most places.)
It is probably wise to work with a lawyer to come up with an end user agreement for the service that protects both parties.
If you are talking about technology to prevent copying, this is mostly useless, especially for text and images although is somewhat successful for streaming video, see Silverlight and Flash.