The first printed books kept their notes in the margin, right where the reader needed them.1 Footnotes only took over when typesetting got fussy about columns, and endnotes arrived when publishers decided notes were too expensive to set on the page at all.

On the web we inherited the worst of both: a tiny number that jumps you to the bottom of the page and a back link you have to hunt for.2 Margins are free on a wide screen, so notes can live beside the sentence they belong to, the way Edward Tufte sets them in his books.3 Hover a number to peek, click to keep it open.

None of this needs a new format. The notes are still written inline, where the author thought of them, and the page decides how to show them from the room it has.