How to navigate to an index.html with nginx?
Did you only try to reach localhost? Or even 0.0.0.0 or 127.0.0.1?
Depending on the operating system, docker config and the internal networking setup, some problem can occurs to reach the docker network.
You can inspect the container to get the network IP, maybe you can go there https://stackoverflow.com/a/20686101/2904965