Error starting userland proxy: listen tcp 0.0.0.0:80: bind: An attempt was made to access a socket in a way forbidden by its access permissions

[vijayverma]

This is because your IIS or some other server is already running on port 80.
Try this and it should work.
docker run --detach --publish 81:80 --name webserver nginx

Then in browser try http://localhost:81/