I’ve worked on websites for several years, both professionally and for side projects. One day, I reflected on the fact that all of my web development education had come from actually making websites. In most cases, I’d have a specific problem, Google how to solve it and learn something new in the process.
I wondered what I was missing by never learning HTML in a comprehensive way. Forget CSS and JavaScript. I’m just talking about raw HTML. It might seem silly to go back to such a basic aspect of web development after a decent amount of experience, but it’s easy to become overconfident with a skill just because you know enough to do a few useful things.