This looks mostly like CSS hack (even the little bit of JS there seems to mainly query the DOM and apply styles). Such things should IMO be packaged as userstyle files. I think people need to be reminded of the concept of userstyles, and how useful they are to remove the garbage web designers produce.
Stylus is a godsend: https://github.com/openstyles/stylus. Sad thing is, this used to be a built-in browser feature.