As we have already discussed, elements in a document occur in a sort of hierarchy. At the most basic level, block-level elements contain other block-level elements, inline elements, and replaced elements. A part of this hierarchy scheme depends on the relationships between these types of elements; for example, while inline elements can be children of block-level elements, the reverse is not true.
In CSS, elements are grouped into three types:
Elements such as paragraphs, headings,
Replaced elements, such as images and form inputs, can be block-level
elements but usually are not. Each block-level element is displayed
on a line by itself, so to speak, beginning on a new line and forcing
any element after it to do the same. Block-level elements can only be
children of other block-level elements, and then only in certain
SPAN, and most replaced elements, such as images
and form inputs. They do not force anything to start on a new line,
not even themselves, and can be the children of any other element.
Elements that in HTML pretty much
include only the
LI element. These are specially defined to have presentation aspects such as a “marker” (a bullet, letter, or number) and a certain sense of ordering, if such an element appears within an ordered list of some kind. Thus, list items within such a list can be automatically numbered, based ...