.login-center{
  position: relative;
  top: 50px;
  height: 170px;
}
#container img {
  position: absolute;
  z-index: -1;
  top: 0px;
  left: 0px;
  width: 100px;
  opacity: 0;

  -webkit-animation: opacity 8s linear infinite;
  -moz-animation: opacity 8s linear infinite;
  animation: opacity 8s linear infinite;
}

@keyframes opacity {
  5%, 25%  { opacity:1; }
  0%, 30%, 100% { opacity:0; }
}

@-moz-keyframes opacity {
  5%, 25%  { opacity:1; }
  0%, 30%, 100% { opacity:0; }
}

@-webkit-keyframes opacity {
  5%, 25%  { opacity:1; }
  0%, 30%, 100% { opacity:0; }
}

#container img:nth-child(1) {
  -webkit-animation-delay: 0s;
  -moz-animation-delay: 0s;
  animation-delay: 0s;
}

#container img:nth-child(2) {
  -webkit-animation-delay: 2s;
  -moz-animation-delay: 2s;
  animation-delay: 2s;
}

#container img:nth-child(3) {
  -webkit-animation-delay: 4s;
  -moz-animation-delay: 4s;
  animation-delay: 4s;
}

#container img:nth-child(4) {
  -webkit-animation-delay: 6s;
  -moz-animation-delay: 6s;
  animation-delay: 6s;
}