1. Delete the \Documents\IISExpress folder using the following console command: rmdir /s /q "%userprofile%\Documents\IISExpress"
2. Delete the applicationhost.config file which is placed within the \.vs\Config\ folder in your Visual Studio project root folder.
3. Close Visual Studio and re-start it with Administrative priviledges (right-click > Run as Administrator).
4. 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.
5. 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/