Just try this:
1) Copy any text by ctrl+c
2) Click the Link:
http://chiragmehta.info/chirag/ViewingClipBoardText.htm
3) You will see the text you copied on the Screen which was accessed by this web page.

Do not keep sensitive data (like passwords, creditcard numbers, PIN etc.) in the clipboard while surfing the web. It is extremely easy to extract the text stored in the clipboard to steal your sensitive information using a combination of JavaScript and ASP (or PHP, or CGI) and then to write your possible sensitive data to a database on another server.

Hopefully you haven’t copied a credit card number recently before surfing!