I don't remember where i found this script to disable right click using javascript.

<script language="JavaScript">
function disableRightClick(e)
{
  var message = "Right click disabled";
 
  if(!document.rightClickDisabled) // initialize
  {
    if(document.layers)
    {
      document.captureEvents(Event.MOUSEDOWN);
      document.onmousedown = disableRightClick;
    }
    else document.oncontextmenu = disableRightClick;
    return document.rightClickDisabled = true;
  }
  if(document.layers || (document.getElementById && !document.all))
  {
    if (e.which==2||e.which==3)
    {
      alert(message);
      return false;
    }
  }
  else
  {
    alert(message);
    return false;
  }
}
disableRightClick();
</script>