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}
If the link in the example above has been visited, it will be displayed in red.
source: http://www.w3schools.com/css/pr_pseudo_hover.asp
