Answer by jbigman for IIS express applicationhost.config security is reset every time a solutions is opened in VS2012

You can edit IIS authentification modes by changing

1. iis properties in \My Documents\IISExpress\config\applicationhost.config

2. project properties in visual studio

The second option is your answer.

A full answer with screenshots is already on stackoverflow : https://stackoverflow.com/a/7168308/2988788