.center_text { text-align:center; }

.page_header 
  {
  background-color: #333;
  color: white;
  padding: 15px 20px;
  position: fixed;      /* Keeps the header at the top */
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;        /* Keeps it above other elements */
  }

  .nav_bar { text-align:center; }

  .nav_bar a
  {
      color:white;
      margin-left:3vw;
      margin-right:3vw;
      text-decoration:none;
  }