I have struggled this a lot! I was very close to not entering Repeat the Ending in Spring Thing 2023, if you can believe that.
I did finally get something going, and I kept adding images until I found sizes that worked most of the time. I edited the CSS until I managed the modest stying changes I wanted. I downloaded “python”—which I had previously only as a snake—and ran a mysterious script.
It worked out in the end, but it was very close, and harrowing, too.
I never used the off-the-shelf Inform stuff again. Maybe Inform 11 will be different!
For the next six releases of Repeat the Ending, I used the Parchment IF Site Generator that Dannii made.
For my more recent games, I used Bisquixe, which allows authors to inject specific bits of CSS a web release without having to understand a ton of CSS. I went back and rereleased Repeat the Ending with Bisquixe, too. My next game will be a Bisquixe game. I’m used to the required python thingy by now, and I’m happy with how those games look. These are the web versions on my itch.io page.
For a basic, defaults-only website, I can’t say enough good things about the Parchment generator. It made it possible for me to quickly fix bugs and update the post-Thing version of RTE.