// addEvent and removeEvent
// cross-browser event handling for IE5+,	NS6 and Mozilla
// By Scott Andrew
function addEvent(elm, evType, fn, useCapture) {
	if (elm.addEventListener) {
		elm.addEventListener(evType, fn, useCapture);
		return true;
	} 
	else if (elm.attachEvent) {
		var r = elm.attachEvent("on"+evType, fn);
		return r;
	}
}

function initCaptcha() {
	var commentform = document.getElementById('commentform');

	if(!commentform) {
		return;
	}

	addEvent(commentform, 'submit', checkCaptcha);
}

function checkCaptcha(event) {
	var rightAnswer = 4;
	var question = "2х2";
	var comment_2x2 = document.getElementById('comment_2x2');

	if(comment_2x2.value != rightAnswer) {
		alert("Введите правильное значение " + question + "!");
		
		// Отменяем Submit формы
		if(!event.preventDefault) { //IE
			event = window.event;
			event.returnValue = false;
		}
		else { // не-IE
			event.preventDefault();
		}
	}
}

addEvent(window, 'load', initCaptcha);