Home page appearance not reflected in published version

I recently published part of my vault with Obsidian Publish, but the appearance of the Home page is not accurately reflected in the published version. For example, the Home page should have a background colour and a banner, but these do not appear in the published version.

Do I need to tweak the publish.css? If so, how?

Also, is there some recommended online resource where I can learn about the very basics of CSS so that I don’t need to ask such elementary questions on this forum?

I eventually found the answer to my first question here.