function textZoom(direction) {
  var diff = 1;
  if(direction == false) {
    diff = -1;
  }

  $('pageTitle').setStyle({fontSize: parseInt($('pageTitle').getStyle('font-size'))+diff+'px'});
  $('pageBody').setStyle({fontSize: parseInt($('pageBody').getStyle('font-size'))+diff+'px'});

  var size = parseInt($('pageBody').getStyle('font-size'));
  setFont($('pageBody'), size);
}

function setFont(tag, size) {
  tag.setStyle({fontSize: size+'px'});
  var childs = tag.childElements();
  for (var index = 0, len = childs.length; index < len; ++index) {
    var item = childs[index];
    setFont(item, size);
  }
}