div.sending[makeform="true"]::after {
    content: " ";
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 100%;
    background: url("images/loading.gif") rgba(255, 255, 255, 0.6) no-repeat;
    background-position: center center;
    z-index: 5;
}

div.sending[makeform="true"] {
    position: relative;
}