#loader {
  position: fixed;
  left: 50%;
  top: 50%;
  border: 4px solid #f3f3f3;
  border-top: 4px solid #3498db;
  border-radius: 50%;
  width: 50px;
  height: 50px;
  animation: spin 2s linear infinite;
}
/* Safari */
@-webkit-keyframes spin {
  0% { -webkit-transform: rotate(0deg); }
  100% { -webkit-transform: rotate(360deg); }
}
@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}