"Standard Module Format" is a way of laying out markup to maximize the "hooks" for styling and scripting in order to allow the maximum flexibility in design.

Each module has a common "mod" class applied (so standard margins / borders / etc can be applied). Each module also has a unique ID namespaced to allow easy customization of a specific region of the page.

Within each module, a header (hd), body (bd) and footer (ft) are added. If one of these elements is not conceivably required, it may be omitted.

Based on this structure, elements can be selected based on their location on the page (generally "header", "content", "secondary" and "footer") - so a module then can become agnostic to it's location. As long as all modules follow the same markup pattern, they can be more easily transplanted throughout the page with very little (if any) changes.