CSS style sheets have a habit of growing big and chaotic over time.
There are a lot of rules, hints, and schools of thought that help achieving cleaner CSS. (For example here) However, all those require constant alertness, activity and a lot of discipline on the maintainer's end, with mixed real-world success. As Nicole Sullivan so nicely puts it:
In fact, in most cases, the things we considered best practices were leading to the bad outcomes we sought to avoid. I realized (unpopular though it might be), that we couldn’t make it work out well by trying harder. Each time we start a new project, we think “this time, I’m going to keep the code clean. This time the project will be a shining example of what can be done with CSS.” And without fail, over time, as more content and features are added to the site, the code becomes a spaghetti tangle of duplication and unpredictability.
Are there any efforts to create a language of some sort, with strict structural rules and a merciless compiler, that enforces strict rules that prevent style sheets from becoming spaghetti? The compiled end result would be CSS.