From http://www.w3schools.com (Copyright Refsnes Data)

CSS :link pseudo-class

Definition

The :link pseudo-class adds a special style to an unvisited link.

Examples

A link that is active, visited, unvisited, or when you mouse over a link can all be displayed in different ways in a CSS-supporting browser:

a:link {color: #FF0000}     /* unvisited link */
a:visited {color: #00FF00}  /* visited link */
a:hover {color: #FF00FF}   /* mouse over link */
a:active {color: #0000FF}   /* selected link */

Note: a:hover MUST come after a:link and a:visited in the CSS definition in order to be effective!!

Note: a:active MUST come after a:hover in the CSS definition in order to be effective!!

Note: Pseudo-class names are not case-sensitive.

Note: Pseudo-classes can be also be combined with CSS classes:

a.red:visited {color: #FF0000}

<a class="red" href="css_syntax.asp">CSS Syntax</a>

If the link in the example above has been visited, it will be displayed in red.

Try-It-Yourself Demos

Hyperlink
This example demonstrates how to add different colors to a hyperlink in a document.

Hyperlink 2
This example demonstrates how to add other styles to hyperlinks.

Complete CSS Reference