docker running splash container but localhost does not load (windows 10)
You have mapped the port to your docker host (the VM), but you have not port-forwarded that same port to your actual "localhost" (your Windows host)
You need to declare that port-forwarding in the Network settings of your VM (for instance "default"), or with VBoxManage controlvm commands.
Then and only then could you access that port (used by your VM) from your Windows host (localhost).
That or you can access that same port using the IP address of your boot2docker VM: see docker-machine ls.
@user3768495, when you use http://192.168.99.100:8050/ , you are actually using the docker-machine ip and this ip would be available on your machine only and not on the network. To map it to localhost, you do need to port-forward the same port to your localhost. I was having the same issue and I detailed the process in below link.