var tabSize = ['0.5em', '0.6em', '0.7em', '0.8em', '0.9em'];
var increase_size = function() {
	divPage = document.getElementById('page');
	var i = tabSize.indexOf(divPage.style.fontSize);
	if (i < tabSize.length) {
		var i = i + 1;
		divPage.style.fontSize = tabSize[i];
	}
	return false;
}

var decrease_size = function() {
	divPage = document.getElementById('page');
	var i = tabSize.indexOf(divPage.style.fontSize);
	if (i < tabSize.length) {
		var i = i - 1;
		divPage.style.fontSize = tabSize[i];
	}
	return false;
}