(The following demonstration text is from Dave Liepmann’s own example.)
Although paper handouts obviously have a pure white background, the web is better served by the use of slightly off-white and off-black colors. Tufte CSS uses #fffff8 and #111111 because they are nearly indistinguishable from their ‘pure’ cousins, but dial down the harsh contrast. We stick to the greyscale for text, reserving color for specific, careful use in figures and images.
In print, Tufte has used the proprietary Monotype BemboSee Tufte’s comment in the Tufte book fonts thread. font. A similar effect is achieved in digital formats with the now open-source ETBook, which Tufte CSS supplies with a @font-face reference to a .ttf file. In case ETBook somehow doesn’t work, Tufte CSS shifts gracefully to other serif fonts like Palatino and Georgia.
Also notice how Tufte CSS includes separate font files for bold (strong) and italic (emphasis), instead of relying on the browser to mechanically transform the text. This is typographic best practice.
If you prefer sans-serifs, use the sans class. It relies on Gill Sans, Tufte’s sans-serif font of choice.
Links in Tufte CSS match the body text in color and do not change on mouseover or when clicked. Here is a dummy example that goes nowhere. These links are underlined, since this is the most widely recognized indicator of clickable text. Blue text, while also a widely recognizable clickable-text indicator, is crass and distracting. Luckily, it is also rendered unnecessary by the use of underlining. However, because most browsers’ default underlining does not clear descenders and is so thick and distracting, the underline effect is instead achieved using CSS trickery involving background gradients instead of standard text-decoration. Credit goes to Adam Schwartz for that technique.
As always, these design choices are merely one approach that Tufte CSS provides by default. Other approaches, such as changing color on click or mouseover, or using highlighting or color instead of underlining to denote links, could also be made to work. The goal is to make sentences readable without interference from links, as well as to make links immediately identifiable even by casual web users.