If you have made changes to Advanced font settings like increasing the minimum/default font size then try the default minimum setting "none" and the default font size 16 in case the current setting is causing problems. *Tools > Options > Content Fonts & Colors > Advanced > Minimum Font Size (none) Make sure that you allow pages to choose their own fonts. *Tools > Options > Content Fonts & Colors > Advanced: [X] "Allow pages to choose their own fonts, instead of my selections above" It is better not to increase the minimum font size, but to use an extension to set the default page zoom to prevent issues with text not being displayed properly. You can use an extension to set a default font size and page zoom on web pages. *Default FullZoom Level https://addons.mozilla.org/firefox/addon/default-fullzoom-level/ *NoSquint https://addons.mozilla.org/firefox/addon/nosquint/ If you have extensions that place toolbar buttons on the Add-on Bar then you need an extension to restore this toolbar. *Classic Theme Restorer: https://addons.mozilla.org/firefox/addon/classicthemerestorer/ *https://support.mozilla.org/kb/what-happened-to-the-add-on-bar