Rated 4 out of 5 stars

Does what it says, and seems to work with some of the tab coloring extensions. Does not support offline files for some reason.

This review is for a previous version of the add-on (0.3). 

Offline?

Hmm, I'm not sure what you mean by offline files. If you mean html pages saved locally and accessed via the file:// protocol, than sure, no favicons are generated for those, since the seed of the icon is the domain name. No domain name, no icon, its that simple. (Localhost, however, does get a favicon.)