<body>
  <div id="divScroll">
    <img src="gora.png" alt="W górę" class="scrollimgs"
         onclick="resizeText('dataDiv', '+', 1, 'pt');"/>
    <img src="dol.png" alt="W dół" class="scrollimgs" 
         onclick="resizeText('dataDiv', '-', 1, 'pt');"/>
  </div>
  <div id="dataDiv" style="font-size:12pt;">
    <!-- tutaj tekst warstwy -->
  </div>
</body>