An arrangement for generating page and/or device-optimized cascading style sheets (“CSS”) is disclosed in which CSS blocks are provided in a collection of one or more files. In an illustrative example, the collection of files is arranged as XML (extensible Markup Language) files. Each CSS block is marked with attributes that indicate to which modules used to compose a page it applies, and/or its applicability to a specific device. At page rendering time, the CSS for the page is dynamically generated by selecting CSS blocks from the files based on detected device capabilities and/or the modules on the page.