The document discusses object-oriented CSS (OOCSS) as a way to improve performance, code reuse, and maintainability of CSS code for websites and applications. It outlines several principles of OOCSS including creating reusable CSS components, separating container and content rules, extending objects by applying multiple classes, avoiding location-dependent styles, and separating structure from skin. Examples are provided to illustrate these concepts. The goal of OOCSS is to write more modular, predictable and maintainable CSS code.