With the PDK, applications can be programmed in C/C++, along with OpenGL ES 1.1 or 2.0, and libraries can be included by statically building/linking them to the executable.
HTML, which stands for Hyper Text Markup Language, is the de facto language of the Web. Nearly all Web pages are composed of some for of HTML. In the Mojo SDK HTML is used for building the scenes that are displayed. Read more about it on the HTML page.
CSS, or Cascading Style Sheets, is a method of describing the presentation of information contained in an HMTL scene. CSS is used to change the appearance of your scenes. Not only can you style all the HTML you add to scene but also the styling of Mojo widgets. Read more about it on the CSS page.