<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<style>
.dropdown-submenu {
    position: relative;
}

.dropdown-submenu .dropdown-menu {
    top: 0;
    left: 100%;
    margin-top: -1px;
}
</style>
</head>
<body>
   
<div class="container">                                       
  <div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">ΑΠΟΥΣΙΕΣ-ΚΑΘ/ΣΕΙΣ
    <span class="caret"></span></button>
    <ul class="dropdown-menu">
      <li><a tabindex="-1" href='allagidate.php'>ΑΛΛΑΓΗ ΗΜΕΡΟΜΗΝΙΑΣ</a></li>
      <li><a tabindex="-1" href='allageshmeras.php'>ΕΜΦΑΝΙΣΗ ΑΛΛΑΓΩΝ ΗΜΕΡΑΣ</a></li>
	  
      <li class="dropdown-submenu">
        <a class="test" tabindex="-1" href="#">ΑΠΟΥΣΙΕΣ ΚΑΘΗΓΗΤΩΝ<span class="caret"></span></a>
        <ul class="dropdown-menu">
          <li><a tabindex="-1" href='#' onClick="popupCenter('apousieskath.php')">ΑΠΟΝΤΕΣ ΚΑΘΗΓΗΤΕΣ</a></li>
          <li><a tabindex="-1" href="#">2nd level dropdown</a></li>
          
        </ul>
      </li>
    </ul>
	<button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">ΠΛΗΡΟΦΟΡΗΣΗ
    <span class="caret"></span></button>
    <ul class="dropdown-menu">
      <li><a tabindex="-1" href='apallagesrep.php'>ΑΠΑΛΛΑΓΕΣ</a></li>
      <li><a tabindex="-1" href='locate.php'><span>ΕΝΤΟΠΙΣΜΟΣ ΜΑΘ.</span></a></li>
  </div>
</div>



</body>
</html>