You can add code to the userChrome.css file below the default @namespace line.

• http://kb.mozillazine.org/userChrome.css

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

.tabbrowser-tab[pinned] { width: 45px !important; }
.tab-label-container[pinned] { visibility: hidden !important; }

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

Hi, Thanks for those instructions. I made it to the point where I would actually add the code (I created a .css file in a chrome folder). I began reading the Adding Style Recipes page, but I'm afraid I got lost among the unfamiliar terms: recipes, XUL vs XML, namespaces, agent sheets. There's advice to not use the code in the first line you provided above to avoid glitches. Different ways to approach adding code... I gave up! Sorry, but is it possible to give me the exact text I can paste into an empty .css file?

You can paste the full text in userChrome.css.

It is not that difficult to create 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 (name is case sensitive). In this 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 .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 file.

See also:

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