Responsive web site design is the practice of laying out your website with DIVs and CSS rules to work seamlessly on both desktop and mobile devices. Responsive designs transform the same content using CSS to linearize layouts, hide features, and create mobile-friendly buttons and click-to-call features useful on mobile devices like tablets and smartphones. This article shows a case study of PhiladelphiOrthodontists.com which was converted from a static HTML site to a WordPress responsive site.