Annotation/Blog Comment that is associated with a specific Paragraph (Paragraph Addressable), and appears next to it in the Margin.

cf Node Web

Often used in 3rd party Annotation Systems.

Can do them for your own Thinking Space

Sidenotes For Web Design ยท (Gwern Branwen)

Comparison of sidenotes implementations for web pages

Similar approaches (some of these are more limited than Tufte-CSS; typically, authors fail to handle narrow/mobile):

(2019-10-04) Nielsen Matuschak How Can We Develop Transformative Tools For Thought: 2019 (mobile: floating footnotes)

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