For years Pharo has had a variety of frameworks for developing web applications. However web applications make use not only of HTML and JavaScript but also CSS, and until recently there was no framework or library for programmatic generation of CSS. RenoirSt was created to fill that gap and allow better integration between CSS and the web frameworks. RenoirSt provides a domain-specific language (DSL) and a set of abstractions modeling the cascading stylesheet components, allowing a better integration with the development environment, reusing the available refactoring tools, and generating static files for deployment. In this talk I will present RenoirSt: A brief description of the DSL, the major abstractions, applied principles of design, practical examples of integration into the environment and lessons learned from carrying out an open source project.