I am reporting feedbacks from France, where great frustrations appear for a certain number of versions, while Mozilla regularly breaks the user interface, and we have to paddle behind that to get it back with CSS work. Not everybody is able to do that, so we have to help each other with that. But sometimes we have real work to do, or lifes to live, and we cannot exist only to keep on using Firefox, that is not reasonable. Some say they would eventually choose another browser, others already did.
I had one user enthusiastically confirming my sum up, but what I say is based on years of participation to mozfr.org. He insists that the instability of the DOM is annoying as the CSS rules he got are no more available.
After reading the forum here on discourse.mozilla.org, I realize many others feel the same, but I shall say it just in case Mozilla does not want to die from autism.
It appears the most frustrations that appeared and had to be regularized with CSS were as follows. Some already are corrected, but deserve to be mentioned to avoid regression.
Two main points motivate the use of CSS : the place where elements appear, and the size of display.
A. Place of elements
A1. Order of the bars on top of the window
A1.1 Title bar, visible or not
A1.2 Menu bar, visible or not
The three following elements are listed in a particular order, but it would be highly preferable the user can order them as he chooses, this is important.
A1.3 Address bar (URL)
A1.4 Personal bar
A1.5 Tabs bar
The three options proposed for the visibility of the personal bar in the last version are very good.
A2. Address bar and search bar : on the same bar, or on different bars
A3. Status bar : always visible, or visible when it has something to display (here again, to be chosen by the user, please)
B. Display size (mainly font sizes)
This has to be developed in as many styles as exist, the idea is to adapt to different visual acuities.
A few users would really appreciate the possibility to have more numerous toolbars, to get their buttons at good places without reducing the display of important elements as the URL.
In case of need some more precision can be given. I develop CSS sheets, maybe I should not have for a too long time to develop themes.
We should like to keep on using Firefox, please do not prevent us from that.