As the name suggest, the PrefBar requires a browser of the Mozilla family (i.e. Firefox, Mozilla Suite or SeaMonkey). Installation is done using an XPI file, which means that a running browser is required. Performing a system-wide installation as root is possible, however updating the browser usually requires a re-installation of the PrefBar.
The PrefBar is a toolbar placed below the so-called Personal Toolbar. It consists of check boxes, drop down lists, buttons, links and a fancy separator. The elements of the toolbar can be changed by right-clicking on the PrefBar, leading to an easy-to-use configuration interface.
If you use your browser in different environments such as on a notebook at work and at home, it may be necessary to change the proxy settings. If you don't want to use different profiles, the PrefBar provides a drop down list to select the desired proxy host. Another case where this is useful is when you want to use an anonymous network such as Tor to access a single webpage.
Sometimes it may be useful to change the User-Agent string, which is how the browser calls itself when accessing a website. This can help if a site creator has designed a moronic browser switch, which bars users of specific browsers from viewing the site. And in other cases it may be quite interesting what happens if you pretend to be the Googlebo ...
Other features include the resizing of the browser window to predefined values and various buttons for opening a new browser tab, saving the page, deleting all stored cookies or clearing the cache. It is possible to add links to the PrefBar, however it is more convenient when using bookmarks for this. Local applications may be launched from the PrefBar as well, specific examples on how to do this are given.
In some aspects the PrefBar adds a new experience to surfing the web. It relieves the user from several problems everybody knows, especially when dealing with the products of incompetent web designers. Beyond that, the PrefBar offers some unique features and it will be interesting to see what will be added in future versions.