This is a web-based game and usually web application consist of backend (located on a server) and frontend (drawn in a browser) apps. If you don't need to make a complex rich application then backend will be just enough. For this you need to know some server-side language like Python/PHP/JavaScript. In my opinion Python is the best choice and here you can find a really good book:

Then you need to use some framework to base you backend on. There are Django/Flask/Bottle, I think that Django is simple enough for quick start and to get some understanding you can try their tutorial:

or just read docs:

Also need to know HTML/CSS and JavaScript, but they are quite simple and there are a lot of info in the net, like: