I finally found a great solution (I think) to solve my problem:
html:
<div id="inner"></div>
<div id="global">
</div>
css:
#global{
margin: 0px auto;
width: 300px;
height: 300px;
position:relative;
top: 0px;
background-color: #ff0000;
z-index: -1;
}
#inner{
width:100px;
height: 100px;
position: relative;
background-color: black;
margin: auto;
z-index: 2;
left: 150px;
top: 50px;
}
Here is the updated fiddle: http://jsfiddle.net/pF4Qx/4/
Hope this will help someone ;)