Friend, try the code below:
<html><head>
<script language="JavaScript"></script></head>
<body onload='clp_clear()'>
<center><font color=darkgreen><font size=3><p>
...Press the [PrintScreen] or the [Alt+PrintScreen] key and try to paste the content in your favorite Picture Editor (Paint,...)...<br>
...Select text and try to paste the content in your favorite Text Editor (Notepad,...)...<p><font color=black><font size=2>
This small script clears the clipboard at runtime and disables screen capture process...but does not disable text selection..</center>
<hr>for more Ambesha blog, please visit <a href="http://ambeshdevloper.blogspot.com/">http://ambeshdevloper.blogspot.com/</a>[<a href="http://ambeshdevloper.blogspot.com/" target="_blank" title="New Window">^</a>] </body></html>
Please let me know if you want any specific...or server side code but in best practice for this task client scripting is appropriate. (please rate this reply)
Thanks,
Ambesha