Yes, it should work, but now you have to enter about:config in the URL bar and set toolkit.legacyUserProfileCustomizations.stylesheets = true.

Hi TyDraniu, tried your solution, but still no success :(

Checked userChome.css file path: C:\Users\<username>\AppData\Local\Mozilla\Firefox\Profiles\<profilename>.default\chrome\ -> seems OK.

CSS contains: @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

1. fullscr-toggler { display:none!important; }

(Hope the hash (#) on the 3rd line doesn't mean it is some kind of a comment...)

checked about:config and the toolkit.legacyUserProfileCustomizations.stylesheets value is set to true

Restarted Firefox, loaded some page, switched to fullscreen and Firefox still shows menu and address bar when mouse near the top of the screen :(

Thank you, but I still have no luck..

CSS FILE: @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

1. fullscr-toggler { display:none!important; }

There is not "1." but the "hash" symbol..

Well, that works for me.

Try to remove the first line.

There is only

#fullscr-toggler { display:none!important; }

Hi TyDraniu, unfortunately, still no success :( I removed the first line, closed other browser panels, disabled all browser addons, tried to empty browser cache just for to be sure and restarted the browser.. but nothing changed, it does not works.

The AppData\Local location is the wrong location for the profile folder. The main profile folder is in "AppData\Roaming".

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/Profiles

It is not that difficult to create userChrome.css if you have never used it.

The first step is to open the "Help -> Troubleshooting Information" page and find the button to access the profile folder.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

You can find this button under the "Application Basics" section as "Profile Folder -> Open Folder". If you click this button then you open the profile folder in the Windows File Explorer. You need to create a folder with the name chrome in this folder (name is all lowercase). In the chrome folder you need to create a text file with the name userChrome.css (name is case sensitive). In this userChrome.css text file you paste the text posted. On Mac you can use the TextEdit utility to create the userChrome.css file as a plain text file.

In Windows saving the file is usually the only time things get more complicated because Windows can silently add a .txt file extension and you end up with a file named userChrome.css.txt. To avoid this you need to make sure to select "All files" in the dialog to save the file in the text editor using "Save File as".

You need to close (Quit/Exit) and restart Firefox when you create or modify the userChrome.css file.

See also:

• https://www.userchrome.org/what-is-userchrome-css.html
• https://www.userchrome.org/how-create-userchrome-css.html

Hi cor-el, I moved the whole chorme folder to the roaming profile path and it works like a charm, of course. It was my mistake, that I created the chrome folder in the AppData\Local profile..

Thank you very much - problem solved

You're welcome