This following code, taken from LissaExplains, will prevent people from rightclicking on the page. This is to prevent people from stealing images, etc.
If you want for there to be a popup alert message when someone right clicks, use the following code:
<script language="JavaScript" type="text/javascript"> <!-- // No rightclick script v.2.5 // (c) 1998 barts1000 // barts1000@aol.com // This script and others available free at http://www.lissaexplains.com var message="Sorry, that function is disabled.\n\nContents & Graphics Copyright İyour name\nOur work is not Public Domain, and should NOT be taken from this site."; // Message for the alert box // Don't edit below! function click(e) { if (document.all) { if (event.button == 2) { alert(message); return false; } } if (document.layers) { if (e.which == 3) { alert(message); return false; } } } if (document.layers) { document.captureEvents(Event.MOUSEDOWN); } document.onmousedown=click; // --> </script>

If you just want people to not be able to right click WITHOUT a message, use this code:
<script language=JavaScript> <!-- var message=""; /////////////////////////////////// function clickIE() {if (document.all) {(message);return false;}} function clickNS(e) {if (document.layers||(document.getElementById&&!document.all)) { if (e.which==2||e.which==3) {(message);return false;}}} if (document.layers) {document.captureEvents(Event.MOUSEDOWN); document.onmousedown=clickNS;}else{document. onmouseup=clickNS;document.oncontextmenu=clickIE;} // --> </script>