how to get started

Can anyone give me a tip on how to get started on the API. what language can the application be written in? I saw there is a xml section and javascript. Could i use html and javascript?

There is a XML and JSON section.

JSON != javascript

You can use any language. But if you want a web application, you need a server-side language as weel.
Something like JSP or PHP. Html an javascript are only on the client side.