I think there's a problem with forwarding requests between the server and the browser that you're seeing - that browser is running locally on your machine, but that server is running in a linux container on some remote machine possibly without its own public ip, so there's some voodoo going on to make localhost refer to that server. Voodoo broken.
I'd do it on my own machine. Not looking to defend codecademy, but doing it in your own environment would be a good thing. If you have a choice then I suggest using a linux machine (less chance of trouble and that's where it's "meant" to run anyway) Keep asking if you have questions about doing that.