This document introduces Diazo, an open source theme engine for bridging web designers and developers. It discusses how Diazo works by using XML rules and XSLT to transform unthemed HTML content into themed content. It provides examples of common rules for replacing elements, including and dropping content, and merging navigation. Diazo allows maintaining design templates separately from dynamic content and deploying transformed content through an XSLT processor. The conclusion recommends starting with example codes, using the editor for common tasks, and keeping organizational themes consistent.