If you mess up the CSS, you might be no longer be able to restore a working version, because the buttons are no longer visible.
Notes for security:
Open two browser tabs.
In tab 1, open https://www.whonix.org/wiki/MediaWiki:Common.css. Then press "edit".
In tab 2, open https://www.whonix.org/wiki/MediaWiki:Common.css as well. Make your edits in tab 2. See how they look like. And if something totally breaks, so you cannot fix it in tab 2 anymore, go back to tab 1 and just press "Save page".
This is a wiki. Want to improve this page? Help is welcome and volunteer contributions are happily considered! See Conditions for Contributions to Whonix, then Edit! IP addresses are scrubbed, but editing over Tor is recommended. Edits are held for moderation.