Reponsive layouts -- Adapting layouts to smaller screens -- may in some cases only be enabled in Webkit browsers to match support in mobile device email apps. You may need to use Safari or Chrome to view mobile-friendly layouts. All layouts are responsive.
CB indicates Clearbold designs (vs development based on provided comps). With many of these examples we've been called upon to "work our magic" and make traditional layouts responsive.
CM indicates Campaign Monitor integration support as well.