What languages to learn for creating a game like Club Penguin?

I am wondering, in today's world, what is best way to go about creating a game like Club Penguin? What languages and server service should I use for creating a browser game like this? I have had a lot of cool thoughts about creating a game like this for a while (and I know it's not easy or cheap) and I actually want to go ahead and attempt to make it and learn the best technologies available for creating said game. Thanks for your help! :)