A standard (or rule set) is contained two principal parts: the selector followed by one Declarations. The guidelines at that point apply the declarations inclined to all components coordinated by the selector. A selector is the piece of the CSS rule that matches HTML components. Selectors can contain at least one straightforward selector, for example, type, class or ID selectors isolated by combinators, which clarify the connection between the selectors. The Declaration is the element that sits inside the curly braces. It comprises a property name followed by a colon, at that point a property value.