the userChrome.css file brings the advanced user the options to bring back old design of firefox, adjust height and color and style of menus, buttons, multirow bookmarks, bookmarks below tabs or above tabs etc.
from time to time, no idea why, the new version of firefox brings with it a change in design and also in the way the userchrome file is understood.
thanks to some nice guys at github this problems is mostly solved fast.
but every time it is work to be done.
and although i understand the need for updates and new designs can be useful and nice,
every single time the programmer team violates the habbits of the user wishes.
why not bring the options of the userchrome file to the preferences menu.
with all design adjustments embedded in firefox, the user can finally decide how firefox should look like for him or her.
once done, stored within preferences and not violated by updates.