Screen display and printing (or any sort of paged media) require different approaches to designing the layout.

The size and aspect ratio of a screen display may change depending on the display environment, so it is hard to know how to accurately specify the size and arrangement of the layout target. The style specification should consider using relative dimensions to accommodate various environments.

In printing, there is an expectation that formatted objects are arranged neatly on fixed-sized pages, therefore, the layout specification should precisely control the layout by specifying absolute dimensions for the size and position of the formatting objects, starting with the size of its characters.