SharePoint 2010 introduces new branding features including the ribbon UI, modal dialogs, rich text editing, and responsive zone orientations. Themes are now defined in the THMX format rather than SPThemes.xml. The CSSRegistration control allows custom CSS to be registered and ordered, including conditional expressions and placement after core stylesheets. Master pages can be customized through SharePoint Designer, Visual Studio, or by deploying features. The "Visual Upgrade" helps transition 2007 master pages but a long term solution is migrating branding to the V4.master.