prueba con
Código CSS:
Ver original.fog
{
width:100%;
height:100%;
opacity: .5;
background: url('/Styles/Images/fog.png') repeat-x center center;
-webkit-animation-name: circulos;
-webkit-animation-duration: 120s;
-webkit-animation-iteration-count: infinite;
-webkit-animation-timing-function: linear;
}