<style>
.picture {position:relative; width:150px; height:150px;}
.picture a {display:block; width:100%; height:100%;}
.picture a img {width:100%; height:100%;}
.picture a span.overlay {diplay:none; postion:absolute; left:50%; top:50%; display:block; width:48px; height:48px; margin-left:-24px; margin-top:-24px; background:url(images/zoom-icon.png) no-repeat;}
.picture a:hover span.overlay {diplay:block;}
</style>

<div class="picture">
	<a href="#">
		<img src="#" width="150" height="150" alt="" />
		<span class="overlay"></span>
	</a>
</div>