The concept of “not breaking the web” is one of its oldest and most foundational. When we build a web page, we do it knowing that it could theoretically last as long as the internet itself. The CSS we write today is, or should be, future-proof. But how will your CSS hold up in 10, 50, or even 100 years? In this talk, we’ll cover how to write CSS that stands the test of time. From progressive enhancement techniques to accessibility considerations, we’ll learn how to write CSS for 100 years in the future (and, of course, today).