You should be learning HTML5!

Beautiful web apps are built with HTML5, CSS3, and JavaScript.

HTML structures a website and also contains data for the website's content, CSS polishes things up with style to make them better looking, and JavaScript libraries take advantage of HTML5 APIs. These three languages are very easy to get started with. There are various neat libraries and tools you can use to quickly build HTML5 mobile apps or browser-based games, and they're often designed to be very beginner-friendly so you don't have to be an expert to build a simple, fun app.