From CSS Discuss
Maintainable CSS often contains the premise of being semantic and having a clear separation occurring on all of the layers within a page. Readable code is often strong in its maintainability, so descriptive ordering is suggested. Ordering rules according to a defined system and having indenting denoting hierarchy are ways to achieve this. Alphabetizing property-value pairs, using validators when significant CSS coding has been completed, and before migrating code to production are just a few of the ways to make your coding sustaining even when you're not around.
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