.ui-loader-background {
    width:100%;
    height:100%;
    top:0;
    margin: 0;
    background: rgba(0, 0, 0, 0.3);
    display:none;
    position: fixed;
    z-index:10000;
    background-image: url('../img/loading-spin.gif');
    background-repeat: no-repeat;
    background-position: center;
}

.ui-loading .ui-loader-background {
    display:block;
}

img.lazy {
     /* optional way, set loading as background */
     background-image: url('../img/loading-spin.gif');
     background-repeat: no-repeat;
     background-position: 50% 50%;
}