Really great guide that seems to nail some of the basics. I can tell the difference between a great reading experience and a mediocre one, but I can never seem

Really great guide that seems to nail some of the basics. I can tell the difference between a great reading experience and a mediocre one, but I can never seem to pinpoint the reason for that difference. Is there a tool that "evaluates" a page for some of these typography basics on a live website? Maybe a bookmarklet. I know at some point it becomes a matter of looking with a trained eye and personal preference, but many of the parameters could easily be computationally evaluated. E.g. measure, line height and paragraph spacing, color/contrast, maybe even visual hierarchy.