YIKES! Seems like a relatively-simple concept like browser FONT preference has become unnecessarily complicated.
I left Safari a couple of years ago when all I wanted to do was have newly-added BOOKMARKS automatically list in alphabetical order when added to a specific bookmark's folder. Instead, after adding, I would have to drag it to its alphabetical position within the folder. Small potato, yes. But a nuisance.
I contacted APPLE (like suggested above) about how to set this in Preferences. Never heard back from Apple. Or install an ADD-ON or PLUG-IN? At the time, no such beast existed, so I have not returned to Safari (went to Opera and now am using Chrome).
Just wondering Safari Users : Does a newly-added bookmark now automatically sort alphabetically into the folder to which it is assigned?
P.S. Chrome has a Preference Option to customize its web browser fonts to whatever one prefers (i.e. choice of font, colour, size, etc.) as well as the ZOOM option. Simply.