Do divs have sizes?

AnotherMe  wrote Do dives have sizes?

Sure they do.  In simplest terms, a division is a box.   Refer to the CSS Box Model.

A division's size is its width + margins + padding + borders.  Height is determined by content inside the box.  Thus there's no need to set explicit height values on divs that contain content.

In responsive layouts, we typically give divisions a % width instead of fixed pixels.  But there are times when you might need to use other CSS Units .