One of the most distinctive features of Tufte’s style is his extensive use of sidenotes. Sidenotes are like footnotes, except they don’t force the reader to jump their eye to the bottom of the page, but instead display off to the side in the margin. Perhaps you have noticed their use in this document already. You are very astute.
This is a side note. Notice there is a number preceding the note.
Sidenotes are a great example of the web not being like print. On sufficiently large viewports, Tufte CSS uses the margin for sidenotes, margin notes, and small figures. On smaller viewports, elements that would go in the margin are hidden until the user toggles them into view. The goal is to present related but not necessary information such as asides or citations as close as possible to the text that references them. At the same time, this secondary information should stay out of the way of the eye, not interfering with the progression of ideas in the main text.
Sidenotes consist of two elements: a superscript reference number that goes inline with the text, and a sidenote with content. To add the former, just put a label and dummy checkbox into the text where you want the reference to go, like so:
You must manually assign a reference id to each side or margin note, replacing “sn-demo” in the for and the id attribute values with an appropriate descriptor. It is useful to use prefixes like sn- for sidenotes and mn- for margin notes.
Immediately adjacent to that sidenote reference in the main text goes the sidenote content itself, in a span with class sidenote. This tag is also inserted directly in the middle of the body text, but is either pushed into the margin or hidden by default. Make sure to position your sidenotes correctly by keeping the sidenote-number label close to the sidenote itself.
If you want a sidenote without footnote-style numberings, then you want a margin note. This is a margin note. Notice there isn’t a number preceding the note. On large screens, a margin note is just a sidenote that omits the reference number. This lessens the distracting effect taking away from the flow of the main text, but can increase the cognitive load of matching a margin note to its referent text. However, on small screens, a margin note is like a sidenote except its viewability-toggle is a symbol rather than a reference number. This document currently uses the symbol ⊕ (⊕), but it’s up to you.
Margin notes are created just like sidenotes, but with the marginnote class for the content and the margin-toggle class for the label and dummy checkbox. For instance, here is the code for the margin note used in the previous paragraph:
This is a margin note. Notice there isn’t a number preceding the note.
Figures in the margin are created as margin notes, as demonstrated in the next section.