@keyframes fade {
  0%   {opacity: 1; display: block; }
  25%  {opacity: 1;}
  30%  {opacity: 0; display: none; }
  100% {opacity: 0;}
}

@keyframes start {
  0%   {opacity: 1; display: block; }
  50%  {opacity: 1;}
  60%  {opacity: 0; display: none; }
  100% {opacity: 0;}
}

#slideshow .one {
  animation: fade 20s linear 6s infinite alternate;
}

#slideshow .two {
  animation: fade 40s linear 10s infinite;
}

#slideshow .three {
  animation: fade 40s linear 20s infinite;
}

#slideshow .four {
  animation: fade 40s linear 30s infinite;
}