etherpad-lite/src/static/css/pad/gritter.css

#gritter-container {
  position: absolute;
  bottom: 0;
  right: 50%;
  transform: translateX(50%);
  text-align: center;
  z-index: 9999;
}

.gritter-item.popup {
  position: relative;
  max-width: 450px;
  visibility: visible;
  right: auto;
  left: auto;
  top: auto;
  bottom: auto;
}
.gritter-item .popup-content {
  display: flex;
}
.gritter-item .gritter-content {
  flex: 1 auto;
  text-align: center;
}

.gritter-item .gritter-close {
  align-self: center;
}

.gritter-item.error .popup-content {
  color: #a84341;
  background-color: #eed3d4;
}