header.php

<nav class="navbar navbar-fixed-top navbar-dark bg-colored">
  <div class="container text-xs-center">
    <button type="button" class="icon-button float-xs-left h-100" aria-label="Calendar" autocomplete = "off" id="sidebar-left-button">
      <span class="icon-navbar icon-calendar" aria-hidden="true"></span>
    </button>
    <a class="navbar-brand" href="index.php">Alma Mater Studiorum<br/>Università di Bologna</a>
    <button type="button" class="icon-button float-xs-right" aria-label="History" autocomplete = "off" id="sidebar-right-button">
      <span class="icon-navbar icon-bell" aria-hidden="true"></span>
    </button>
    <!--<button type="button" class="icon-button float-xs-right">
      <svg viewBox="0 0 99 99" class="icon-navbar" xmlns="http://www.w3.org/2000/svg" >
        <use xlink:href="fonts/icons.svg#bell"></use>
      </svg>
    </button>-->
  </div><!-- /.container -->
</nav><!-- /.navbar -->