If you've developed an application with the Messenger Library, you're probably aware that when you are testing your application locally, in the past you've had to go through the trouble of providing a hosts entry with a valid domain name and then using that value when instantiating the SignInControl object. This obviously is a hassle when you're behind a proxy and testing on IE, Firefox and other browsers since each needs to be configured uniquely. To simplify your experience, we've recently added support for 'localhost' so that you can easily test your app on your machine. Once you publish your application on the Internet, you'll need to update it with your actual domain name, but hopefully this change will get you going more quickly. Please let us know if you have any questions or comments. Your continued feedback is greatly appreciated.