HTML and CSS Reference
8.3.6. Class Inheritance
Classes inherit the style properties of their generic base tags. For in-
stance, all the properties of the plain <p> tag apply to a specially defined
paragraph class, except where the class overrides a particular property.
Classes cannot inherit from other classes, only from the unclassed ver-
sions of the tags they represent. In general, therefore, you should put
as many common styles as possible into the rule for the basic version of
a tag and create classes only for those properties that are unique to that
class. This makes maintenance and sharing of your style classes easier,
especially for large document collections.