Type That Reads Well: Scale, Line Length and Pairing

Text reads well when its sizes come from a type scale in rem, its lines hold about 45 to 75 characters, its line height suits body text and headings, and the page uses two fonts at most.

Updated

Cheat sheet: Type That Reads Well: Scale, Line Length and Pairing
Category
CSS
Level
Journeyman
Tags
CSS, Font pairing, Font size, Letter spacing, Line height, rem unit, Type scale, web-development