The page chrome://browser/content/browser.xhtml shows the whole Firefox UI, which you can use to work on your userChrome.css, and inspect with Dev Tools (rather than the Browse Toolbox in a separate w

The page chrome://browser/content/browser.xhtml shows the whole Firefox UI, which you can use to work on your userChrome.css, and inspect with Dev Tools (rather than the Browse Toolbox in a separate w

The page chrome://browser/content/browser.xhtml shows the whole Firefox UI, which you can use to work on your userChrome.css, and inspect with Dev Tools (rather than the Browse Toolbox in a separate w