function checkPropergation(e) {

	if (navigator.appName == 'Netscape' && (e.which == 3 || e.which == 2)){
		
		return false;
	}else if (navigator.appName == 'Microsoft Internet Explorer' && (event.button == 2 || event.button == 3)) {
		alert("Sorry, you do not have permission to right click.");
		return false;
	}
	return true;
}

function setUp(){

	if(window.document.getElementById('mask')){
		
		addEvent(window.document.getElementById('mask'),'mousedown',checkPropergation);
		addEvent(window.document.getElementById('mask'),'mouseup',checkPropergation);
	}
	

}