function randomString() {
	var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz";
	var string_length = 8;
	var randomstring = '';
	for (var i=0; i<string_length; i++)
	{
		var rnum = Math.floor(Math.random() * chars.length);
		randomstring += chars.substring(rnum,rnum+1);
	}
	return randomstring;
}
function keepAlivePing()
{
   var img = document.createElement("img");
   img.src = "/keepalive.php?" + randomString();
}
window.setInterval(keepAlivePing, 45000);