I run both T-bird 45.3.0 and Firefox 48.0.1 on my 2014 Mac Air/El Capitan. My laptop was lagging and dropping the network signal, so I shut it down for about 20 minutes. When I powered it back up, the fonts on both Firefox and Thunderbird were reduced almost to the point of unreadability. Focusing just on Tbird for a moment: I opened Preferences, where everything looked normal. As an experiment I raised the minimum font size up to 24 pts. No change. It's all still miniscule - both the list display and the email contents. (On Firefox, it's the tabs and toolbars.) I have the Theme Font and Size Changer Add-on. I disabled, re-enabled, removed, and re-installed it. Nothing. I've tried to open Preferences for it but all I get is a radio button list: - Hide Tools Menu option - Hide App Menu option - Abbreviate Toolbar Button Text ... nothing about the actual font size. What's gone wrong here, and how do I get back to readable font? Thanks!