rev1: Toggling visibility of the URL bar and tabs via the bookmarks toolbar visibility setting [SELF-SOLVED]

 visibility: collapse;

Just wanted to drop in here and give an update to my original post detailing how to hide the tabs and address bar when in fullscreen mode, using the View/Toolbars/Bookmarks Toolbar/Never Show command. With this css in place and the preferences set, toggling the bookmarks toolbar in fullscreen mode will toggle everything at the top of the FF window (but won't do that unless fullscreen is active). This code changed recently (like, today) because the "collapsed" attribute from the #PersonalToolbar item no longer toggles between "true" and "false" when the user hides/shows the toolbar — instead, the "collapsed" attribute disappears entirely when the toolbar is showing, and reappears to be assigned the value "" (yes, empty) when the toolbar is hidden. --- Here's the CSS. It goes into a text file called "userChrome.css". :root[sizemode="fullscreen"] #navigator-toolbox:has(#PersonalToolbar[collapsed=""]) { visibility: collapse; } --- On the Mac, here's the location. The CSS file then goes into a "chrome" folder in the "Profiles" folder located within your Mac user account's "Library" folder (not the Profiles folder within the Library folder on the root of the system drive, but the one in your computer account Home folder). You'll probably need to create the chrome folder. Just put the CSS above into a text file, name that file "userChrome.css" and drop it in the location shown below. Quit Firefox first, of course. /Users/<user>/Library/Application Support/Firefox/Profiles/<profile>/chrome/ --- You'll also need to set the about:config options in Firefox to allow legacy user profile customizations. Go to about:config in the browser, and search for "toolkit.legacyUserProfileCustomizations.stylesheets" and set this preference to "true". --- The code only updated slightly today. See my original "question" here: https://support.mozilla.org/en-US/questions/1448596#