A points on many HTML tags (aside, mark, section, hgroup, video, progress, base): how to use them. Many good tips or rules to follow.
The CSS @import rule, [attr$=value] is a CSS selector for suffix values, box shadows with inset, cursor: zoom-in

Translated pages with <link rel="alternate"> and hreflang

Some usages such as HTML in script to reuse them as <template />, gpt or instappaper_ignore class names

The web is big and messy and bloated, and there are lots of reasons to be pessimistic about the state of modern web development – but there are also lots of people doing cool and interesting stuff with it.