var pageurl = location.href;

var clickmessage= 'Picture and Caption are copyrighted. \n \n If you want to use the picture on a Blog or a web site, \n \n Please place a link to this URL on your web page: \n \n ' + pageurl + ' \n \n Thanks'  

document.oncontextmenu = disableRightClick;

function disableRightClick()
{
  alert(clickmessage);
}