For Web Research (Webliography) and (Collaborative, public or private) Web Annotation I rely on https://web.hypothes.is/
Started using it in January and I've gone over 2100 annotations 800 odd is public the rest is private
https://hypothes.is/users/gyuri
Best thing since slice bread and can be used to annotate online pdfs too.
Its worth saving pages at the wayback machine and annotating the saved page, that so that if the web page disappears (life expectancy of a link is 100 days on average) you still have a way to refer to it and your annotations remains live