Modal popupextender with Login form

[dianna]

I want to take this opportunity to introduce a sample application which shows how to use the ModalPopupExtender for logging and signup for any ASP.NET web application. In this quick demonstration, I am going to show you how we can implement a modal dialog box using AJAX in ASP.NET. A modal dialog box (formally called a ModalPopupExtender) is extremely essential in today’s applications as it avoids redirecting to a new page just to login or signup users. A simple example is shown here illustrates how to implement the same.
Background

I was looking around to see samples of how to use the ModalPopupExtender for login and signup for my site...but I could not find any. So finally, I ended up creating this login sample application so it might be useful for everyone.
Using the Code

To start with, let's try to understand the ModalPopupExtender.