Not saying its the best one but I built a system we used on the NYTimes web site for awhile that was fault tolerant and adjusted to changes in the page: https:

Not saying its the best one but I built a system we used on the NYTimes web site for awhile that was fault tolerant and adjusted to changes in the page: https://github.com/NYTimes/Emphasis https://github.com/NYTimes/Emphasis