This is source. 
<!DOCTYPE html>
<html>
<head>
<meta name="viewport"
content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=no">
<meta name="format-detection" content="telephone=no">
<style>
html,body {
margin: 0;
}
.gnav {
  width: 100%;
  background: #141414;
  overflow-x: auto;
  overflow-y: hidden;
  -webkit-overflow-scrolling: touch;
  position: fixed;
}
.gnav ul {
  width: 800px;
  margin: 5px auto 7px auto;
  list-style: none;
  display: flex;
}
.gnav ul li {
    text-align: center;
}
.gnav ul li a,
.gnav ul li a:link,
.gnav ul li a:visited {
  display: inline-block;
  width: 96px;
  background: #141414;
  color: #fff;
  text-decoration: none;
}
.gnav ul li a:hover,
.gnav ul li a:active {
  background: #141414;
}
</style>
</head>
<body>
<div class="gnav">
<ul>
<li><a href="#">menu1</a></li>
<li><a href="#">menu2</a></li>
<li><a href="#">menu3</a></li>
<li><a href="#">menu4</a></li>
<li><a href="#">menu5</a></li>
<li><a href="#">menu6</a></li>
<li><a href="#">menu7</a></li>
<li><a href="#">menu8</a></li>
</ul>
<!--gnav--></div>
</body>
</html>