Most XHTML 1.0 elements permitted within the body are classified as
either block-level elements or inline elements. Block-level elements typically
contain inline elements and other block-level elements. When
rendered visually, block-level elements usually begin on a new
line.
The following are defined as block-level elements in
XHTML 1.0:
The following elements may be used as either block-level
elements or inline elements. If used as
inline elements (e.g., within another inline element or a
p), these
elements should not contain any block-level elements.