How to fix - Firefox 4.0 Beta : browser.tabs.tabMinWidth doesn't work

find the firefox profile :

find . -name userChrome*

./Library/Application Support/Firefox/Profiles/mahk6fwf.#02/chrome/userChrome-example.css

cd "./Library/Application Support/Firefox/Profiles/mahk6fwf.#02/chrome/"
cp userChrome-example.css userChrome.css
vim userChrome.css

(Append to the end of the file :)

.tabbrowser-tab[fadein]:not([pinned]) {
    min-width: 18px !important;
  }

:wq

restart firefox

reference :
http://www.lawlzoids.com/proxy/?__new_url=aHR0cHM6Ly9idWd6aWxsYS5tb3ppbGxhLm9yZy9zaG93X2J1Zy5jZ2k/aWQ9NTc3NDk3

http://support.mozilla.com/bn-BD/questions/745380