body{
 background-repeat: no-repeat;
 background-attachment: fixed;
 background-size:cover;
 background-image:url("grulla_21.jpg");
 background-position: top;
}

#ihead{
 width:100%;
height:100vh;
}

#courtain{ 
  background-color:black; 
  background-size:cover; 
  width: 100vw;
  position:fixed;
  z-index:100;
  top: -50vh;
  }

article.mod{
  position:fixed;
  z-index:0;
}

p.mod{
  color:black;
  font-weight:bold;
  font-size:1.3em;
  max-width:500px;
  padding:5% 5%;
  text-align:left;
  }