How non-conforming (invalid) HTML can give us a headache?

If you're thinking that we are using MUI and we do not need to know these details I should say that the way I see it is when you know building blocks of a system, its mechanisms, and how they work together as a whole can change your life for the better. Do not believe me? Read these slides and see how debugging strange looking issues are when you are aware of what's going on behind the scene.

Besides just by knowing HTML spec we can prevent hours of debugging, It can also be a real life saver when you do not have any clue about something but just by reading their examples you might get an idea of what you need to do.

This is in fact one of those areas that soft skill and hard skill collide and we have these beautiful situations.

Lemme know your thoughts in the comments.

Here is where you can learn more about HTML/CSS.

And here is where is the source of truth

And as for a browser, here you can find where blink's parser is parsing the document.