I'm setting up an online form where to choose boxes and stuff. I almost finished the whole thing when I said to my self "Let's try it in IE".

This is the result I want and what comes up in Google Chrome:

And this is what happens in IE:

And this is the CSS and HTML for that part:

<!--- HTML --->
<div id="choosen"><img src="img.jpg" class="center-img" /></div>


/* --- CSS --- */
img.center-img{
    margin-top:15px;
    position:relative;
    width: <?php echo $width; ?>px;
    left:50%;
    margin-left:-<?php echo $width/2; ?>px;
}

Basically the image is centered into the div as this page I'm writing will be included into another one which I never saw and someone else will do it.