There are websites and browser extensions (such as https://chrome.google.com/webstore/detail/page-monitor/pemhgklkefakciniebenbfclihhmmfcd?hl=en https://chrome.

There are websites and browser extensions (such as https://chrome.google.com/webstore/detail/page-monitor/pemhgklkefakciniebenbfclihhmmfcd?hl=en https://chrome.google.com/webstore/detail/page-monitor/pemhg... ; haven't used it myself though) that keep track of diffs of pages, but they require that a user first decides to watch a particular webpage. Is this what you are looking for or are you looking for something that tracks news stories automatically? (useful if you want to see how an article changes before you saw it or if you want to discuss changes within a community.)