How popular web designing was even 5 or 10 years ago. Kids in computer institutes were teaching themselves HTML and building small web pages from scratch. Nowadays this is possible because of the thousands of free tutorials and codes online. Open source has dramatically shaped an industry of high-tech and high demand.
But it can still be crucial pinpointing exactly what you need to learn. Beyond straight HTML/CSS there is jQuery for frontend animation, PHP/RoR for backend web apps, and even Java/Objective-C for mobile apps. Here are some useful websites that can guide the freelance web designers to learn about web development. With this collection you should be capable to track down a few tutorials in whatever topic grabs your interest.