When you run the ASP.NET development server out of Visual Studio, you may be prompted by Firefox or IE for a username and password before you can continue.
The following solutions worked for me using Windows 7, Visual Studio 2008 & 2010 with Firefox 3 and Internet Explorer 8.

The problem
I recently used the calendar control from the AJAX toolkit to set a date in its associated textbox control. I wanted the user to only be able to set the date through the calendar control so I made the textbox read only by setting the ReadOnly property …