With Visual Studio 2010 Beta1, we introduced a new feature called Web.Config transformation to help ease the development process of a web application. At different stages during the life cycle of a project, the user usually needs to modify some environment settings in the web.config file such as connection strings, application settings,... It can be hard to keep track of those settings and time-consuming to do so manually if the user keeps switching between development stages often. With the Web.Config transformation feature, the user can modify the web.config file seamlessly according to various server environments. Vishal has written a blog to provide detail about how to user this feature "Web Deployment: Web.Config Transformation".
SDET, Visual Web Developer