var currentFontSize;

function default_text_size(){
	currentFontSize = 12;
	change_text_size(0);
}

function large_text_size() {
	currentFontSize = 14;
	change_text_size(+2);
}

function small_text_size() {
	currentFontSize = 10;
	change_text_size(-2);
}

function change_text_size(sizeDifference){
	currentFontSize = parseInt(currentFontSize) + parseInt(sizeDifference);
	if(currentFontSize > 14){
		currentFontSize = 14;
	}else if(currentFontSize < 10){
		currentFontSize = 10;
	}
	set_font_size(currentFontSize);
}

function set_font_size(fontSize){
	var stObj = document.body;
	if (stObj) {
		stObj.style.fontSize = fontSize + 'px';
	}
}