UserChrome.css and userContent.css

"userChrome.css" and "userContent.css" are CSS files that can be used to tweak the user interface and styling of web pages in Mozilla-based applications, like Firefox, Thunderbird, Mozilla Suite, Nvu etc.

These files must be located in "chrome" subfolder in your profile folder. They don't exist by default—you must create them. There usually are two example files, "userChrome-example.css" and "userContent-example.css", in the same folder; you may just rename them.

userChrome.css and userContent.css are read on application startup only, so for any changes in those files to take effect, you have to restart the application.

The ChromEdit extension can be used to easily edit these files and also user.js without the need to find the profile folder.

See also

• Editing Configuration Files at Firefox Help
• Editing Configuration Files at Thunderbird Help

/* Remove autocomplete dropdown */

1. PopupAutoComplete > .autocomplete-tree { display: none !important; }