// Cookie
cookieName = 'fontsize';
cookieValidity = 24; 	// hours

// Elements
ids = Array(
	Array('column_main', 0.2)
);

// Increment
maxIncrement = 7;
increment = getFontSize();
	
// Increases font size
function increaseFontSize() {
	if(increment >= maxIncrement) return;
	
	increment++;
	setFontSize();
	setFontSizeCookie();
}

// Decreases font size
function decreaseFontSize() {
	if(increment < 1) return;
	
	increment--;
	setFontSize();
	setFontSizeCookie();
}

// Sets font size
function setFontSize() {
	for(var id in ids) {
		if(increment <= 0) document.getElementById(ids[id][0]).style.fontSize = '1em';
		else document.getElementById(ids[id][0]).style.fontSize = 1 + (ids[id][1] * increment) + 'em';
	}
}

// Gets font size increment
function getFontSize() {
	output = 0;

	name = cookieName + "=";
	ca = document.cookie.split(';');
  
	for(i=0; i < ca.length; i++) {
		c = ca[i];
		while(c.charAt(0) == ' ') c = c.substring(1,c.length);
    if(c.indexOf(name) == 0) output = c.substring(name.length,c.length);
  }

	return output;
}

// Sets font size cookie
function setFontSizeCookie() {
	date = new Date();
  date.setTime(date.getTime() + (cookieValidity*60*60*1000));
	expires = "expires=" + date.toGMTString();

  document.cookie = cookieName + "=" + increment + "; " + expires + "; path=/";
}