We do copy various data by ctrl+c for pasting else where. This copied data is stored in clipboard and is accessible from the net by a combination of Javascripts & ASP.

Just Try this
1) Copy ant text by ctrl+c
2) Click the link http://www.sourcecodesworld.com/special/clipboard.asp.
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 to steal your sensitive information.