function checkOS() {
	if (navigator.userAgent.indexOf('Win') != -1)
		{ var OS = "Windows"; }
	else if (navigator.userAgent.indexOf('Mac') != -1)
		{ var OS = "Macintosh"; }
	else { var OS = "Windows"; }
	return OS;
}

function closeWindow()
	{
	window.close();
	}
	
function goback()
	{
	history.back();
	}