@keyframes reject{
  25%{
    left: 48%;
  }
  75%{
    left: 52%;
  }
}

.login_window{
  padding:10px;
  position: absolute;
  background: #9090ff;
  top:50%;
  left:50%;
  margin-left: -86px;
  margin-top:-51px;
  border-radius:10px;
}
.login_field{
  width: 150px;
  padding:3px;
}

.login_window_reject{
  animation-name: reject;
  animation-duration: 0.5s;
  animation-iteration-count:2;
  animation-timing-function: linear;
}