While getting start with ASP.NET and Visual Studio, you may run into 'Error: Cannot write configuration file' while trying to open an existing project -- for example, our ASP.NET example project. The error looks like this:
To resolve, follow the path to the applicationhost.config file. Right click to on the file to open it's properties, then click on 'Advanced' and uncheck 'Encrypt contents to secure data'. Save your changes, and then try opening the project again.