function logout() {      
	var nosAjaxObject = createXmlHttpObject();
  	if (!nosAjaxObject) {
	   return;
  	}
	
    var url = 'security?do=logout';
    nosAjaxObject.onreadystatechange = function logoutOk() {};
    nosAjaxObject.open("POST", url, true);
    nosAjaxObject.send(null);  	
}