h1 {text-align: center;}
  h2 {text-align: center;}
  p {text-align: center;}
  div {text-align: center;}
  
 .center {
   display: block;
   margin: auto;
   width: 50%;
  }
  
 .Header img {
   margin-top: 70px; 
   float: center;
   width: 256px;
   height: 93px;
  }
  
 .center {
   display: block;
   margin-left: auto;
   margin-right: auto;
   width: 50%;
  }
  
 body {
   background-image: url(https://pacifist.neocities.org/cool_star_flash.gif);
  }
 
 .center {
   display: block;
   margin-left: auto;
   margin-right: auto;
   width: 50%;
 }