#loader{
     position:absolute;
     top:0;
     left:0;
     width:100%;
     height:100%;
     z-index:-1;   
}
#loader.activated{
     background:url('img/wait.gif') center center no-repeat;
     z-index:999;
     
}

#loader.deactivated{
     background:none;
     z-index:1;
}