The idea is to create a program/plug-in so that a reader of a web page can highlight a paragraph or sentence or even type notes. This tool will provide a paper-pencil equivalent that allows reader to take notes right on the reading page.
The program/plug-in can require installation so that it can have permission to work on all tabs.
Given the dynamic nature of web pages, there will be challenges on how to implemented this. One possible solution is to save a static copy on the local machine and apply highlights to it. Once this is done, we can extend this to static pages on the web. Possible examples are the RFCs, the W3C URIs ... etc.
One possible solution for dynamic pages is to use the text-search to locate possible positions. The search may include parsing the XML.
In addition to the page highlighter, a program can monitor changes of the highlighted pages and report to user for maintenance.