Perhaps the most comprehensive and detailed online reference around! If you have a code-related issue, this should be your first point of reference.
One of the more comprehensive resources for code. Caveat emptor: this site tends to give you the entire bucket of Legos, and it’s up to you to know where to find the pieces you need.
Front End Development
Cody Lindley’s master course in all things front-end. A huge, invaluable resource. Strap in.
HTML & CSS Online Courses
A really well done course presented by Shay Howe, a Chicago-based designer and educator. Check out Howe’s advanced course, too! (This one’s in development.)
A basic HTML & CSS course for non-web designers by Jessica Hische & Russ Maschmeyer. The course tackles a lot of the basics through a series of nicely produced videos, and speaks to designers on the level of design rather than strictly through code.
HTML Language Guides
The Mozilla Developer’s Network offers a fantastic set of reference tools that covers the basics of client-side web development. This is their introduction to HTML.
Imaging for Web and Game Development
Have a GIF? Need a sprite sheet? This nifty tool does the trick.
Some really nice experiments related to web typography.
A great primer on the basics of typographic form. See also their “Top 10 Dos and Don’ts of Web Typography.”
If you really love typography—and I mean really love it—you will love these two sites. “I” is a blog; “We” is a gallery. Prepare to lose an hour to this site. You’re welcome.
Smashing Magazine provides a list of prominent and lovely typography blogs for your perusal.
A nice web type blog from the Type Manager for Typekit, Tim Brown.