OOCSS, or Object-Oriented CSS, is a web design methodology that promotes the separation of structure and skin in stylesheets. This approach encourages developers to create reusable components, or "objects," that can be styled independently of their context. By focusing on the functionality of elements rather than their appearance, OOCSS helps maintain cleaner and more manageable code. The main principles of OOCSS include the separation of content from design and the use of reusable classes. This allows for greater flexibility and consistency across a website, making it easier to update styles without affecting the underlying structure. Overall, OOCSS enhances maintainability and scalability in web development.