body {
    background-color: rgb(85, 85, 85);
    margin: 0;
  }

nav {
    position: fixed;
    width: 100%;
    top: 0px;
}

nav ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: #333;
  }

nav li {
    float: left;
    padding: 0;
  }
 
 
nav li a {
    display: block;
    color: white;
    text-align: center;
    padding: 12px 8px;
    text-decoration: none;
  }
  

nav li a:hover {
    background-color: #111;
  }

iframe {
    border: none;
    display: flexbox;
    width: 49.7%;
    height: 315px;
    margin: 0 auto;
}

@media only screen and (max-width: 800px) {
    iframe {
      width: 100%;
    }
  }

h1 {
    margin: auto;
    padding-top: 100px;
    width: 90%;
    max-width: 1024px;
    text-align: center;
    padding-bottom: 30px;
}

h3 {
    text-align: center;
    border-bottom: 1px solid grey;
    padding-bottom: 6px;
}

#general {
    margin: 0 auto;
    width: 90%;
    max-width: 1024px;
}

#physical {
    margin: 0 auto;
    width: 90%;
    max-width: 1024px;
}

#text {
  margin: 0 auto;
  width: 90%;
  max-width: 1024px;
}

#pictures {
    margin: 0 auto;
    width: 90%;
    max-width: 1024px;
}

#videos {
    margin: 0 auto;
    width: 90%;
    max-width: 1024px;
}

#contact {
    margin: 0 auto;
    width: 90%;
    max-width: 1024px;
    padding-bottom: 65px;
}

.container {
    background-color: rgb(255, 255, 255);
    margin: 0 auto;
    width: 100%;
    max-width: 1024px;
}

#pictures .gallery {
    margin: 0 auto;
    width: 90%;
  }
  
#pictures .gallery img {
    width: 100%;
    height: auto;
  }
  
* {
    box-sizing: border-box;
  }
  
#pictures .responsive {
    float: left;
    width: 20%;
    padding-top: 7px;
    padding-bottom: 7px;
  }
  
@media only screen and (max-width: 700px) {
    #pictures .responsive {
      width: 49.99999%;
      margin: 0;
    }
  }
  
@media only screen and (max-width: 500px) {
    #pictures .responsive {
      width: 100%;
    }
  }
  
.clearfix:after {
    content: "";
    display: table;
    clear: both;
  }

  .header {
    width: 90%;
    margin: 0 auto;
    display: flex;
  }