#box
{
    width:300px;
    height:300px;
    text-align:center;
    background: red;
    font-size:42px;
}

span { 
    display: inline-block; 
    position:relative;
}

div.background {

position:absolute;

left:0px;

top:0px;

z-index:-1;

}

div.background img {

position:fixed;

list-style: none;

left:0px;

top:0px;

}

div.background ul li.show {

z-index:500

}

div.background  
{
    position:absolute; 
    left:0px; 
    top:0px; 
    z-index:-1;
    }
    div.background img 
    {
         position:fixed; 
         list-style: none; 
         left:0px; 
         top:-413px;
         }
         div.background ul li.show 
         {
              z-index:500
              }