A collection of links I've found particularly useful or clear on a topic I don't, or didn't at one point, understand. Pull requests welcome!
- CSS Guidelines
- Hacks for Dealing With Specificity
- Atomic Design: Brad Frost
- Fluid Grids: Ethan Marcotte
- where have you gone, Box Sizing, our nation turns its lonely eyes to you, woo woo woo
- About HTML semantics and front-end architecture
- Naming UI Components in OOCSS
- What No One Told You About Z-Index
- MDN: The Stacking Context