.ui-dialog .ajax-progress-throbber {
  position: fixed;
  z-index: 1000;
  top: 48.5%;
  /* Can't do center:50% middle: 50%, so approximate it for a typical window size. */
  left: 49%; /* LTR */
  width: 24px;
  height: 24px;
  padding: 4px;
  opacity: 0.9;
  border-radius: 7px; 
  background-color: #232323;
  background-image: url(/core/misc/loading-small.gif);
  background-repeat: no-repeat;
  background-position: center center;
} 
[dir="rtl"] .ui-dialog .ajax-progress-throbber {
  right: 49%; 
  left: auto;
} 
.ui-dialog .ajax-progress-throbber .throbber,
.ui-dialog .ajax-progress-throbber .message {
  display: none;
}