I no longer use this CSS as I've switched to Firefox-UI-Fix which is much better and maintained properly.

• Tabs aren't floating
• Tabs have a highlight
• More compact (even more compact than Photon compact!)
• Icons on menu
• UI isn't too small or too big

1. Download files
   • Click the green “Code” button above
   • Select "Download Zip”
2. Find your profile directory
   • Open about:support in a new tab
   • Find the Profile Folder entry and click the Open Folder button
3. Copy downloaded files
   • Extract the downloaded zip file
   • Create a new directory inside your profile directory called chrome
   • Copy the remaining files from the extracted zip-file into previously created the chrome directory
4. Firefox Settings
   • Go to about:config an enable toolkit.legacyUserProfileCustomizations.stylesheets
   • Restart Firefox

black7375 for the icons on the menus