Pseudo-classes are used to add special effects to a specific selector.
A hyperlink can be styled using cascading style sheets to have a different appearance, according to its state. The four most commonly supported hyperlink pseudo-classes are listed in the following table:
A hyperlink that has not been visited
A hyperlink that has already been visited
A hyperlink that the pointer is over
A hyperlink that is currently selected
Cascading style sheet rules for hyperlink pseudo-classes will work correctly only when they appear in this order.