Butterick’s Practical Typography for the Web ⇥ practicaltypography.com
Via John Gruber comes this fantastic web-based book about how to set type specifically for pages on the web. While some typographical rules are pretty much universal, the web demands a comprehensive set of rules of its own; Butterick has delivered just such a guide. Tremendous.
Despite his (and others’) recommendations, however, I’m probably going to keep using 13-pixel Neue Helvetica here, because I am a terrible human being.