vertically and horizontally center align image in all browser including ie6

CSS

.image_wrapp{border:1px solid black;width:250px;height:250px;float:left;text-align:center;}

.image_thumb{height:250px;text-align:center;width:250px;line-height:250px;display:table-cell;vertical-align: middle;}

.image_thumb img{vertical-align: middle;}

.image_thumb span {display: inline-block;}

HTML

<li class="image_wrapp">

<div class="image_thumb">

<a href="#"><img src="style/image_thumb.jpg" alt="" /></a><span></span>

</div>

<a href="#">some text </a>

</li>