The structure of the markup is dependent on the semantic structure of the content that is marked up. The CSS is styling that structure. The markup shouldn't ne

The structure of the markup is dependent on the semantic structure of the content that is marked up. The CSS is styling that structure. The markup shouldn't need to change over time in a way that makes the CSS layouts not work because it just reflects the semantic structure of the document, which shouldn't really need to change. If it does you have quite a different document and so of course it will need CSS changes too. I was always much more afraid of touching ad-hoc CSS that was written alongside HTML, because it ends up having all these classes and elements that have no semantics and it becomes very unclear what anything actually means. The very worst is the "tailwind" styling where classes etc mean nothing, just styling.