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I have some modifications I want to make WITHOUT installing extensions.

eg: max width of tab and height of menu,

In previous versions you could have it done via:

about:config ->

Since FF4 it should be done with CSS. Now I searched the default theme:

C:\Program Files (x86)\Mozilla Firefox

In the second I could find the extension -> theme but without any CSS. In the AppData I couldn't find any CSS or theme folder.

WHERE is the file to create or alter the CSS??

I'm using Firefox 11.

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FYI, Stylish is very reliable. – grawity Apr 7 '12 at 12:30
@grawity common, i EXPLICITLY wrote i don't want an addon, i even mentioned that i hate them!! – Email Apr 7 '12 at 13:51
You mentioned that you hate them because they are crappy. They aren't. – grawity Apr 7 '12 at 14:00
@grawity. u seem to be ignorant. READ THE FIRST SENTENCE. "I have some modifications i want to make WITHOUT installing crapy extensions". IN THE TITLE i even declare CSS !! that i thought to be idiot proof but i did forget about you. anyway have a great day. – Email Apr 7 '12 at 14:13
You seriously need to chill a bit. There's a reason @grawity posted this as a comment. He's being helpful. Someone else, who maybe doesn't have your aversions to using plugins, might have a similar problem, and stumble upon this question as part of a web search. That comment will help. Remember, SU isn't your private support hotline, in fact, questions that aren't of general interest will get closed on this site. – Daniel Beck Apr 7 '12 at 14:19
up vote 2 down vote accepted

Go to your Firefox user profile directory. There, open the folder chrome (create it if it doesn't exist) and rename userChrome-example.css to userChrome.css (or create a copy and rename that, like it says right in the file).

Add the following CSS to the file userChrome.css:

.tabbrowser-tab:not([pinned]) {
   max-width: 100px !important;

Save, and you're done.

enter image description here

Some issue comments mention that all of the CSS changes have some flaws though, compared to the earlier preferences. On my system, they tabs to the right (and the new tab button) don't slide to the left when I close a tab at the left side.

enter image description here

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Helped me tremendously (I was trying to set max-width for the url address bar)... if you had bolded "create it if it doesn't exist" for the chrome directory, it would have saved me "idiot search time" (the time it takes for idiots to figure out that they should read a piece of guidance properly, not "internet read" it). – GT. Jul 4 '12 at 23:25

The CSS file is not present at first, you have to create it.

C:\Program Files\Firefox\defaults\profile\userChrome-example.css

Is an an example userChrome.css file, after adding the CSS, save the file as userChrome.css to


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