<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="es" lang="es">
<head>
<meta http-equiv="Content-Type" content="application/xhtml; charset=utf-8" />
<title></title>
<style type="text/css">
.contenedor {
border: 1px solid red;
width: 518px;
height: 320px;
}
.contenedor .oculto{
z-index: 99;
position: relative;
top: -178px; /* mitad height .contenedor + mitad height imagen de fondo */
left: 214px; /* mitad width .contenedor - mitad width imagen de fondo */
width: 89px;
height: 36px;
}
.contenedor:hover .oculto{
opacity: .7;
background-position: center center;
background-image: url("ver_mas.png");
background-repeat: no-repeat;
}
</style>
</head>
<body>
<div class="contenedor">
<a href="descargar.php"><img src="img1.png" alt="fondo" /></a>
<div class="oculto"><a href="vermas.php"><img src="sprite_pixel.gif" width="89px" height="36px" alt="trasparente" /></a></div>
</div>
</body>
</html>