Centering a floating div

[_yo_wasup_]

This is not a fixed width layout. I have one or two CSS techniques applied to these images-- a shadow for all of them which requires floating, and there is also a caption for some of them.

http://matt.mw/gmsaa/articles/passing_in_review3.html

I need to be able to center the last picture "with" the shadow in this layout, but am wondering how to do this. I managed to do it with two images (as you can see at the very top) using 2 divs within another div, but one image is really killing me with floating items.

.img-shadow {
float:left;
background: url(http://matt.mw/gmsaa/img_shadow/shadowAlpha.png) no-repeat bottom right;
margin: 10px;
}
.img-shadow img {
display: block;
background-color: #fafafa;
border: 1px solid #a9a9a9;
margin: -6px 6px 6px -6px;
padding: 4px;
}

<div class="img-shadow"><img src="http://matt.mw/gmsaa/articles/passing_in_review/passing_in_review_images-012.jpg" /></div>

So without taking away this float & shadow, how do I place this image in the exact center when this layout is not fixed? Obviously text-align:center has no effect on floating items. Seems different positioning methods like "absolute" ruin my shadow.

Please help me out! Thanks.

[_yo_wasup_]

I guess I can't edit my post.....

Link update: http://matt.mw/passing_in_review3.html

[Jayhawk]

The following inclodes a bunch of color styling as well as the margin styling for centering, but itshould illustrate the point. The z-index puts the shadowed div behind the other one.

.fshadow {                      /* properties on form shadow */
     width: 400px;
     height: 520px;
     position: absolute;
     left: 50%;
     margin-left: -190px;
     top: 50px;
     background-color: #cdcdcd;
}
.fbox {                        /* properties on form container */
     width: 400px;
     height: 520px;
     position: absolute;
     left: 50%;
     margin-left: -200px;
     top: 40px;
     border-top: 2px solid #910000;
     border-left: 2px solid #910000;
     border-right: 2px solid #6E0000;
     border-bottom: 2px solid #6E0000;
     color: #000000;
     background-color: #FFFFFF;
     font-weight: bold;
     text-align: center;
}

<div class='cbox black p34' style='width:1270px; margin:30px 0; text-align:center'>

     <div class='fshadow' style='width:900px; height:145px; margin-left:-440px; top:150px; z-index:120;'>
     </div>
     <div class='fbox' style='width:900px; height:145px; margin-left:-450px; top:140px; z-index:125;'>
     </div>

</div>