Fantastic add-on, but be sure to use Infocatcher's updated version from GitHub Puntuado con 5 de 5 estrellas
This was *just* the addon I was looking for, so as not to download a ~200MB ZIP file unnecessarily. Fantastic! Only caveat is that the original 0.7.1 version by solar available on this page and on SourceForge doesn't work in FF4+, but the amazing Infocatcher has an updated 0.7.2 version available on GitHub that works brilliantly for me in FF26. Highly recommended!
1) Set up the add-on as shown here: http://i.imgur.com/S1GUNAN.png Be sure to select the "Show icon in the Status Bar" option. In newer versions of FF the icon will naturally show up in the Add-on Bar (Ctrl+/) instead since the Status Bar is long gone.
2. Left-clicking the icon toggles between two states. Here's what they mean: http://i.imgur.com/8SQGDOR.png