Font Inspector is an addon that helps you easily inspect all fonts within a website.
In order to start working with this addon, simply click on the toolbar icon once to open the in-page UI. Then, click on any HTML element that you want to see the font info.
Please note that, as long as the UI is open, no links (or other functions) in the page will work. The in-page UI has several information related to the selected font such as size, style, color, family, etc. Besides, there are information about current tab such as id, width, height, title and url. If you click on the toolbar icon again, the in-page UI will disappear and all the links within the page work as normal.
In order to report bugs, please fill the Bug report form in the addon's homepage (http://mybrowseraddon.com/font-inspector.html).