function increaseFontSize() {
  var elems = document.querySelectorAll('p, blockquote');
  for (i = 0; i < elems.length; i++) {
    if (elems[i].style.fontSize) {
      var s = parseInt(elems[i].style.fontSize.replace("px", ""));
    } else {
      var s = 12;
    } if (s != max) {
      s += 1;
    }
    elems[i].style.fontSize = s + "px"
  }
}