Alternatively,
<style type="text/css">
#example {
display: block;
width: 30px;
height: 10px;
background: url(../images/example.png) no-repeat;
text-indent: -9999px;
}
</style>
<a href="http://www.example.com" id="example">See an example!</a>
More wordy, but it may benefit SEO, and it will look like nice simple text with CSS disabled.