You can "zoom" all sites to a certain default level, such as 80%, using one of these extensions: * [https://addons.mozilla.org/firefox/addon/default-fullzoom-level/ Default FullZoom Level] * [https://addons.mozilla.org/firefox/addon/nosquint/ NoSquint] After setting your Global zoom level, you can still fine-tune the zoom on individual sites using Firefox's standard zoom feature (keyboard shortcut or mouse wheel).

You can set the layout.css.devPixelsPerPx pref on the <b>about:config</b> page to 1.0 or on Windows 8 to 1.25 and if necessary adjust layout.css.devPixelsPerPx starting from 1.0 in 0.1 or 0.05 steps (1.1 or 0.9) to make icons show correctly. *http://kb.mozillazine.org/about:config See also: *https://support.mozilla.org/kb/forum-response-Zoom-feature-on-Firefox-22 Use an extension to adjust the text size in the user interface and the page zoom in the browser window. You can look at this extension to adjust the font size for the user interface. *Theme Font & Size Changer: https://addons.mozilla.org/firefox/addon/theme-font-size-changer/ You can look at the Default FullZoom Level or NoScript extension if web pages need to be adjusted after changing layout.css.devPixelsPerPx. *Default FullZoom Level: https://addons.mozilla.org/firefox/addon/default-fullzoom-level/ *NoSquint: https://addons.mozilla.org/firefox/addon/nosquint/