 <p>In Visual Studio 2010, you now can apply a transformation to your web.config depending on the build configuration.</p> <p>When creating a web.config, you can expand the file in the solution explorer, and you will see two files:</p> <ol> <li>Web.Debug.Config </li> <li>Web.Release.Config</li> </ol> <p>They contains transformation code that can be used to:</p> <ul> <li>Change the connection string</li> <li>Remove debugging trace and settings</li> <li>Register error pages</li> </ul> <p><a href="http://msdn.microsoft.com/en-us/library/dd465326%28VS.100%29.aspx" rel="nofollow">link</a></p>