References
There are thousands of HTML and CSS tutorials dotted around the web. A simple Google search will give you a much better idea of the resources available than any list of references I can provide.
Mike Bostock's website has a wealth of beautiful D3 visualizations: http://bost.ocks.org/mike/. To understand a bit more about D3, I recommend Scott Murray's Interactive Data Visualization for the Web.
You may also wish to consult the references given in the previous chapter for reference books on the Play framework and designing REST APIs.