Here is an example. Click on the link and you’ll see the icon appear.
The code looks like this:
<style type="text/css">
<!–
.visitedlinks a:visited {
background-image: url(http://www.joomlashack.com/university/templates/
js_joomlashacku/images/tick.png);
background-position: right center;
background-repeat: no-repeat;
padding-right:20px;
}
–>
</style>
<div class="visitedlinks">
<a href="#">this is a link
</a>
</div>
Feel free to use it on your own sites!