CSS in the the Custom HTML Head Content is just displayed above the top banner and thus has no effect.
BookStack 0.27.5 hosted on Docker

Hi @essdeeay, can you copy and paste in a comment here the exact content you're using in this setting.
It looks like you just need to wrap you css in style tags, content in that setting gets inserted directly as html.
Ah, I need to close this... I've just found out that the styling needs to be
Most helpful comment
Aha, you replied, just as I found it - thank you - damn fast support!
S :)