Whether you wrote it yourself or not. There was no road, so many people walked, and naturally they got out of the way. This is a fact. Just like before the unified specification was formulated, browsers didn't write it themselves.
The reason why the specification is formed is because the so-called specification is a common form (-_-) for the convenience of viewing, sharing, teamwork and secondary development. Feeling more and more chaotic)
For example, #container changed its name to #bigman, you know, but what about your team? Or after delivery to the customer? With the development in the future, when you look back at this page, you may forget to call yourself #bigman.
But then again, these things are not dead. If you have an online studio and a CSS framework developed by yourself, if you like to call it #main #girl, it's nobody's business. You'll know between you, and you won't fail W3C verification.
Take a small code on Apple's website as an example.
& ltul id = " family-ipad " class = " first-row " & gt；
It's called family -ipad. Obviously, this unordered list is used to store ipad-related content.
By analogy, if there is a rice with enlarged area, it is ok to call it # meter, which is a truth.
# Sidebar and #mainbody mentioned in your supplementary question, the former is common and has a sidebar, while the latter is not very common to me, so the word #main, body is useless, and there is #mainbox.
See for yourself in more detail. It is suggested to look at the foreign literature introduction. Look at the codes of large, standardized and well-known foreign networks, read more and summarize them by yourself, which is smarter than what others say.