SideWiki
Google Sidewiki was a web Annotation tool from Google, launched in September 2009 and discontinued in December 2011. Sidewiki was a browser extension that allowed anyone logged into a Google Account to make and view comments about a given website in a sidebar. Despite the name, the tool was not a collaborative Wiki, though the comments were editable by the author. https://en.wikipedia.org/wiki/Google_Sidewiki
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