html { 
    background: url(bg.jpg) no-repeat center center fixed; 
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(src='images/bg.jpg', sizingMethod='scale');
    -ms-filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='images/bg.jpg', sizingMethod='scale')";
}