CSS

That is a good question. The beauty of the web is that readers can control their experience, be it with ad blockers, increasing the font-size, reader mode, or even changing the whole experience with user style sheets or Greasemonkey. This doesn't mean it's a waste of time to bother with pretty designs. People should build websites that they're proud of, and accept that people might override their design with one better suited to their needs or taste.