The CSS styles in that section have been working spectacularly well for me. The purpose of the styles is of course to display web content that is hidden by JS without having to enable JS. If you disable JS globally and enable it per-site as needed, as you should, and have ever run into a website where the page is completely or partially blank, these styles may solve the problem, and if they don't, send me a link to the page.
There's more code on that page for doing the same with images and YouTube videos, though i'm seeing more and more websites using lazy-loading for images and iframes which often depend on JS, thus there's no convenient way to display them without enabling JS, at least none that i've found so far.
Note that some styles may break some websites, but that seems to happen almost never in my experience.