intro to the wrapup...
everything in this section must be considered, even if you don't have control (not building an OS)... must know what it might do to your design...
even for something as simple as a web page, you should be aware of how little or much room is used by these components; for example scrollbars vary enough you will need to avoid false bottoms, etc. with all normal tools, as you cannot rely on always-visible scrollbars
Or viewports: what if the browser keeps titles and menu tabs visible all the time. That small viewport might be 30% smaller due to these elements, so you cannot try to squeeze everthing to fit...
IMAGE OF ALL COMPONENTS... LABELED WITH NAMES OF PATTERNS