This article presents HSS1 , a compiler for CSS. It is first argued that generating CSS improves portability and maintainability of CSS files. This claim is supported by realistic examples. Then, the HSS compilation algorithm is presented. It is simple enough to be easily adapted to most web development kits. HSS can be used as a stand-alone HSS-to-CSS compiler in the goal of enriching CSS with user defined variables, functions, and element types. It can also be used with the Hop web development kit in which case, working hand in hand with the Hop programming language, it can be used to implement skinning or theming of web applications. Categories and Subject Descriptors D.3.2 [Programming Languages]: Language Classifications—Design languages General Terms Design, Languages Keywords Web programming, Functional languages, Scheme, CSS