  <script type="text/javascript">
    var dataDiv = null;
    var stepX = 3;
    var stepY = 2;
    var szybkość = 50;

    function przesuń()
    {
      var x = parseInt(dataDiv.style.left);
      var y = parseInt(dataDiv.style.top);
      x += stepX;
      y += stepY;
      if(x > 200){x = 200; stepX = -stepX;}
      if(y > 200){y = 200; stepY = -stepY;}
      if(x < 0){x = 0; stepX = -stepX;}
      if(y < 0){y = 0; stepY = -stepY;}
      dataDiv.style.left = x + "px";
      dataDiv.style.top = y + "px";
    }
    function startAnim()
    {
      dataDiv = document.getElementById("dataDiv");
      setInterval(przesuń, szybkość);
    }
  </script>