SiteDelta Highlight от Andreas Schierl

This extension adds a small Delta icon to your browser toolbar. When you click onto it, it allows to highlight all changed text contents of the current page (since the last time you clicked onto it). Clicking again cycles through the changes. Additionaly, you can add scan or ignore regions.

As advanced features (that require additional permissions), you can configure SiteDelta to automatically highlight the changes whenever you visit a known page. Additionally, you can tell SiteDelta to check if any of the known pages has changed.

If you want to be notified about changes without opening a page or manually requesting a check, try SiteDelta Watch. Of course, you can also install both extensions at the same time.