Use either an embedded or external cascading style sheet. Here is an example of an embedded style sheet [insert into head section.]
<style type="text/css">
<!--
a:link {text-decoration: none; }
a:visited {text-decoration: none; }
a:active {text-decoration: none; }
a:hover {color: #800000; text-decoration: underline; background: #008000; }
-->
</style>
a:link is the 'normal, unvisited' state.
a:visited is a link that has been followed b4
a:hover is obvious
a:active is when you press the left mouse button while hovering over a link.