var message = "Photos propriete de BNS, merci de votre comprehension !";

function click(what) {

	if(navigator.appName == "Netscape"){
		 if(what.which == 3){
			alert(message);
			}
		}
	else{
		if (event.button==2 || event.button==1+2)
			alert(message)
		}
	 }
document.onmousedown=click