function logout(url) {
	var xmlhttp = null;
	if (window.XMLHttpRequest) {
  		xmlhttp=new XMLHttpRequest();
  }
	else if (window.ActiveXObject) {
		xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
	}
	if (xmlhttp!=null) {
		xmlhttp.open("GET", url, true);
		xmlhttp.send(null);
	}
	else {
		alert("Your browser does not support XMLHTTP!");
	}
}