Use this handy, simplified guide to quickly learn HTML and CSS -- a foundation of modern web development.

How do I learn to code in HTML and CSS on my Mac? Web design is one of the most useful skills you can learn, and it’s easy to learn HTML and CSS (the two main pillars of web pages) in Mac OS X.

View Source is an iOS app that allows you to do it on any page and includes handy syntax highlighting that makes it easy to find what you need.