Every selector has the potential to have unintended side effects by targeting unwanted elements or clashing with other selectors. More surprisingly, our selectors may even lose out in the global specificity war, ultimately having little or no effect on the page at all. Any time we make a change to a CSS file, we need to carefully consider the global environment in which our styles will sit. No other front end technology requires so much discipline just to keep the code at a minimum level of maintainability.
Last year I wrote about why booking too far in advance can be dangerous for your business, and this concept of margin so eloquently captures what I had recognized had been my problem: I was so booked up with clients that I wasn’t leaving any margin for error, growth, planning, or reflection.