PHP is one of the most popular programming languages today and is used by companies like Facebook, Yahoo, and Wikipedia.
HTML5 / CSS
Learn how to make responsive and visually pleasing websites. Have your web app working on all devices right out of the box.
Iterate fast. Learn how to quickly make MVP's, and create the features that your users actually want.
When scaling efficiency is one of the most important and hardest subjects to tackle.
Make your web app come to life with animations, pop ups, sliders, and modals.
Git / Source Control
Learn how to work as a team on a single code base.