- Delete the DocumentsIISExpress folder using the following console command: rmdir /s /q "%userprofile%DocumentsIISExpress"
- Delete the applicationhost.config file which is placed within the .vsConfig folder in your Visual Studio project root folder.
- Close Visual Studio and re-start it with Administrative priviledges (right-click > Run as Administrator).
- Change the project’s website random URL: within Visual Studio, right-click to the project node in Solution Explorer, then select Properties; navigate through the Web panel, then change the number in the Project Url textbox value.
- Add the _CSRUN_DISABLE_WORKAROUNDS Environment System variable with the value of 1 as shown in the following screenshot (thanks to Juan M. Elosegui for reporting this on this SO thread and for the image):
source:https://www.ryadel.com/en/unable-launch-iis-express-web-server-error-visual-studio-2015-fix/