CSS Methodologies are structured approaches to writing and organizing CSS code, aimed at improving maintainability and scalability. Popular methodologies include BEM (Block Element Modifier), OOCSS (Object-Oriented CSS), and SMACSS (Scalable and Modular Architecture for CSS). Each methodology provides guidelines for naming conventions, file organization, and component-based design, making it easier for developers to collaborate and manage styles in large projects. By adopting a CSS methodology, teams can create a consistent and predictable codebase, reducing the likelihood of conflicts and improving overall efficiency. These methodologies encourage best practices, such as reusability and modularity, which help streamline the development process and enhance the user experience across different devices and platforms.