For a long time I’ve been using userChrome.css to adjust the size of the fonts in the toolbars in FF. Then for some reason it stopped working (FF 72.0.2 on OpenBSD).
After some digging on the internet I found a solution. You need to use “about:config”.
Type this in a new tab. Accept the warning. Then search for “devp”. This has a line:
In my case the default value for this was -1.0. To get acceptable-size fonts I needed to make it 1.8 (i.e. increase it from a negative to a positive value).
To change this, click the pencil symbol on the right and make the change. Then close the tab. (The symbol to the right of the pencil, which is two curved arrows, returns the value to default. At least it does in the current version but all this keeps changing in different versions of Firefox so you may need to experiment.)
Note 1: doing this will change ALL the fonts in FF, so you will probably need to adjust your font size setting in Preferences.
Note 2: As an alternative to all this you can make the fonts bigger in ALL your programs, including Lyx, Gimp, Lowrtier etc. This is probably the best solution if you are using the X-Window system in Unix or linux. To do this add the following lines to ~/.xsession and ~/Xresources:
Xft.dpi: 120 in ~/.Xresources
xrandr --dpi 120 in ~/.xsession
(Use different values instead of 120 if you prefer.)
[Courtesty of Mark Patruck on misc:openbsd.org.]