Building a mobile user interface can be a time consuming process for web site administrators. We present a novel approach for adapting existing websites to the mobile paradigm. In contrast to existing technologies, our approach aims to provide a trio of functionality, ease of use, and scalability for large web communities. A site administrator visually selects objects within a web page, and assigns one or more attributes to page objects from a rich collection of pre-defined page modifications. Our proposed system then generates code for a multi-session, php-based proxy server to provide dynamic mobile content adaptations based on the attributes selected. The modifications encapsulate complex page interactions and provide a simplified interface to mobile users. The proxy server is augmented with a highly efficient and standards-compliant browser residing on the server to interpose on behalf of a resource-constrained mobile client. Adaptations such as pre-rendering of content can be cached and shared across users to amortize load. We build a prototype and evaluate its efficacy on a complex web application driving a busy online community with nearly 66,000 members.