Each style rule in a style sheet has two main parts: the selector, which determines which elements are affected and the declaration, made up of one or more property/value pairs, which specifies just what should be done (Figures 7.1 and 7.2).
Figure 7.1. A style rule is made up of a selector (which indicates which elements will be formatted), and a declaration (which describes the formatting that should be executed).
Figure 7.2. Multiple property/value pairs in the declaration must be separated by a semicolon. Some folks simply end every property/value pair with a semicolonincluding the last pair in a listso that they never forget to add it. That's fine, as shown here, but not required. Note the extra spacing and indenting to keep everything readable.
To construct a style rule: