function increaseFontSize() {
  var className = getClassName();
  if ('font1' == className) {
    d('pagewidth').className = 'font2';
  }
  else if ('font2' == className) {
    d('pagewidth').className = 'font3';
  }
}

function decreaseFontSize() {
  var className = getClassName();
  if ('font2' == className) {
    d('pagewidth').className = 'font1';
  }
  else if ('font3' == className) {
    d('pagewidth').className = 'font2';
  }
}

function getClassName() {
  return d('pagewidth').className;
}

function d(id) {
  return document.getElementById(id);
}