[fstorr] @garcialo: Level AAA’s rules on line height and length more-or-less tie into core design typography best practices. You can cross reference them with Robert Bringhurst’s classic “Elements Of Typographic Style”. That said, if I remember correctly, the AAA requirement for line length is 80–100 characters, but Bringhurst recommends 45–75 (
http://webtypography.net/2.1.2). A line length of 75-80 characters is very readable. Likewise, AAA’s leading/line-height requirement is essentially 1.5em, which is usually the lazy designer’s default (I’ve seen that so many times over the years). Bringhurst recommends choosing "a basic leading that suits the typeface, text and measure” (
http://webtypography.net/2.2.1) which for body copy is usually very close to that size. I will create a typographic scale for a project and then pick a leading that matches, or is very close to, the AAA requirement.