A must have Rated 5 out of 5 stars

A simple, focused, yet very effective little extension, extremely useful.

Once installed, you can add new buttons to the toolbar.
These buttons allows you to go up in the URL hierarchy (one '/' higher or to the root), allowing to explore sites or to quickly go out of a 404 page.
It also has an icon to exploit the "link rel" tags of the page, and next / previous arrows. The latter extract information from the page or the URL to guess the navigation (next / previous page, also first / last pages), and is quite effective. Of course, you often have buttons or links to do that (and they are used by the extension), but too often their place vary in the page and users have to locate them and position the cursor there, which is distracting from the reading. Having these buttons conveniently located on the toolbar at a fixed place is a time saver.