There is an ocean of CSS that mimic off the shelf LaTeX or journal-specific layouts. They're almost entirely one-off attempts depend on a particular HTML structure to have the CSS work. Introducing new CSS layouts to work on the same HTML generally doesn't work well.
In https://dokie.li/ , HTML is key - semantic and sufficiently "flexible". CSS is secondary. That is why we can generally throw different CSS at it without touching the underlying HTML pattern. Examples:
You can dynamically switch the CSS view from the dokieli menu (top-right) or from your browser's native controls eg. view the ACM authoring guidelines using the LNCS CSS and vice-versa.