Bookmarks and Footnotes

Web pages still have too much distracting noise. Even the best sites have too many hyperlinks, both within the text and in the margins with related content. With books you can get away with density in both text and image, but since the Internet promotes skimming, trains of thought are easily broken. With a bookmark one can save their place, but on the Internet, there is no digital bookmark that could be as useful.

Idea: a footnote popup that creates a clickable thumbnail for each link within the text and in the margins, that serves as a visual bookmark or post-it note for each. Does it exist?