<style type="text/css">

h1 {
  animation-duration: 3s;  
  animation-name: slidein;  
}

@keyframes slidein {
  from {
    margin-left: 100%;
    width: 300%;
    color: blue;
    background-color: #aaccff;
  }
  to {
    margin-left: 0%;
    width: 100%;
    color: black;
    background-color: white;
  }
}
</style>