body {
margin: 0;
font-family: Arial, Helvetica, sans-serif;
background-color:#FF0;
background:url( "../IMG/one.jpg" )no-repeat 5% 5%  ;
background-size: cover; 
height: 100vh;
background-position: center;
margin: 0px auto;
background-repeat: repeat-x;
background-attachment: fixed;
}

.topnav {
  overflow: hidden;

  background-color: #333;
}

.topnav a {
  float: left;
  display: block;
 
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-size: 18px;
}

.topnav a:hover {
  background-color: #ddd;
  color: black;
}

.active {
  background-color: #8B0000;
  color: white;
}

.topnav .icon {
  display: none;
}






@media screen and (max-width: 600px) {
  body {
  
  
 
background-color:#FF0;
background:url( "../IMG/one2.jpg" )no-repeat 5% 5%  ;
background-size: cover; 
height: 100vh;
background-position: center;
margin: 0px auto;
background-repeat: repeat-x;
background-attachment: fixed;
}





.topnav a:not(:first-child) {display: none;}
  .topnav a.icon {
    float: right;
    display: block;
  }
}

@media screen and (max-width: 600px) {
  .topnav.responsive {position: relative;}
  .topnav.responsive .icon {
    position: absolute;
    right:  0;
    top: 0;
  }
  .topnav.responsive a {
    float: none;
    display: block;
    text-align: left;
  }
}