Ask HN: What are some must read/learn web design resources for developers?

I've worked as a back-end developer for a small IT firm for some time and am now trying to venture into web design but despite knowing HTML5/CSS3 markup and writing valid markup, I'm finding it hard to dictate to the browsers what I really want. I feel like I'm missing something crucial. Can anyone who made the leap form developer to designer point me in the right direction, please?