It looks like "smallexample" class is used for all? code blocks in the manual.

We also have an emacs specific manual.css: https://www.gnu.org/software/emacs/manual.css

I also quickly looked through https://www.gnu.org/combo.css and https://www.gnu.org/layout.css but didn't find anything related to "smallexample".

But I don't know enough css to say how the smallexample class should be formatted so that it looks good on any browser/screen. Hopefully someone with a know-how on this topic can chime in.