function setFontSize(size) {
  // small, medium, large
  var font_size;
  switch(size){
    case 'small':
      font_size = '12px';
      break;
    case 'medium':
      font_size = '14px';
      break;
    case 'large':
      font_size = '16px';
      break;
    default:
      font_size = '12px';
      break;
  }
  document.body.style.fontSize = font_size;

  if (navigator.cookieEnabled) {
    var c = 'F=' + escape(size);
    c += ';path=/';
    document.cookie = c;
  }
}

function initFontSize() {
  var size = getFontSize();
  setFontSize(size);
}

function getFontSize() {
  var c = document.cookie + ';';
  var n = 'F=';
  var s = c.indexOf(n);
  if(s != -1) {
    var d = c.indexOf(';', s);
    var size = unescape(c.substring(s + n.length, d));
    return size;
  } else {
    return 'small';
  }
}

function addEvent(func) {
  if (window.addEventListener) {
    window.addEventListener("load", func, false);
  } else if (window.attachEvent) {
    window.attachEvent("onload", func);
  }
}

addEvent(initFontSize);