These only apply to the Page Box using the
@Page At-Rule.
What Are They?
Pseudo-classes usually define dynamic states of an element that are
entered and exited over time, or through user intervention. The CSS specs
do not always define which elements may be in a pseudo-class state, or
the method in which the state is entered or exited. CSS2 DOES
state that a browser is not required to re-render a document because
of pseudo-class state transitions however.
Some Pseudo-classes describe mutually exclusive states of an element, while
others describe states or conditions that can exist in parallel to each
other. Pseudo-classes may also classify elements based on other
characteristics that are not directly found in the document element tree
(such as 'first-child'.)
Unlike Pseudo-elements, Pseudo-classes are allowed anywhere in CSS
selectors.