Hacking websites to your needs with UserCSS
A Webbrowser extension like Stylus (Firefox, Chrome) allows you to inject custom website layout and style changes to your needs. You can make use of a huge number of community-published UserCSS or configure your own CSS rules.
I have been using custom CSS on various websites for a long time. It allows me to remove noise, improve UX, and otherwise fit websites to my needs. I also use them at work, and hacked Jira and GitLab to my needs (increase pop-in dialog sizes, decrease irrelevant content size, hide irrelevant content).
Various Webbrowser extensions improve existing websites. FrankerFaceZ for Twich adds a huge number of settings and additional emotes from multiple third-party providers (BTTV, 7tv, FFZ). Augmented Steam adds various useful settings, functionalities, and additional information to store pages like play-through time, price history and comparison, custom notes.
But not every website needs a huge number of improvements, additional settings, or functionality. Custom CSS allows for a wide range of visual, layout, and formatting changes.
I love my nyancat YouTube player progress bar.
As for my own adjustments, I updated my published UserCSSes today, publishing additional ones too. For example UX improvements to Steam, AniDB, itch.io, and IndieGala.