Syntax
CSS has a simple syntax and uses a number of English keywords to specify the names of various style properties.
A style sheet consists of a list of rules. Each rule or rule-set consists of one or more selectors, and a declaration block. A declaration-block consists of a list of declarations in braces. Each declaration itself consists of a property, a colon (:), and a value. If there are multiple declarations in a block, a semi-colon (;) must be inserted to separate each declaration.
In CSS, selectors are used to declare which part of the markup a style applies to, a kind of match expression. Selectors may apply to all elements of a specific type, to elements specified by attribute, or to elements depending on how they are placed relative to, or nested within, others in the document tree.
Pseudo-classes are used in CSS selectors to permit formatting based on information that is outside the document tree. An often-used example of a pseudo-class is :hover, which identifies content only when the user 'points to' the visible element, usually by holding the mouse cursor over it. It is appended to a selector as in a:hover or #elementid:hover. A pseudo-class classifies document elements, such as :link or :visited, whereas a pseudo-element makes a selection that may consist of partial elements, such as :first-line or :first-letter.
Selectors may be combined in many ways, especially in CSS 2.1, to achieve great specificity and flexibility.
Here is an example using the above rules:
selector { property: value; [property2: value2; ...] } /* comment */Read more about this topic: Cascading Style Sheets