.loader {
    position:relative;
}
.loader:after {
    content:'';
    position:absolute;
    z-index:99999;
    border: 4px solid #f3f3f3 ; /* Light grey */
    border-top: 4px solid #3498db ; /* Blue */
    border-radius: 50%;
    width: 30px;
    height: 30px;
    animation: spin 2s linear infinite;
}
@keyframes spin {
   0% { transform: rotate(0deg); }
   100% { transform: rotate(360deg); }
}