<div style="position:relative; float:left; clear:none; overflow:hidden;">
<img src="URL DE L'IMAGE" style="position:relative; z-index:1; width:400px;">
<div style="display:block; position:absolute; width:100%; top:60%; left:0; z-index:2; text-align:center; background:#505050; color:#ffffff; padding-top:5px; padding-bottom:5px; opacity:0.6;">et la petite phrase qui va avec</div>
</div>