I was wondering if someone would mention RSS (or Atom). What I'd like to see is a site that generates diffs from webpage changes, and makes them available as a

I was wondering if someone would mention RSS (or Atom). What I'd like to see is a site that generates diffs from webpage changes, and makes them available as an RSS feed you can subscribe to. Ideally this would be a free service, and I wouldn't mind if the RSS entries were prepended with adverts (or required you to click through to a page hosted by the service in order to see the diff, surrounded by adverts).