function XHR() {
	var xmlhttp = null;
	if (xmlhttp == null) {
		(function() {
			if (typeof XMLHttpRequest != "undefined") {
				xmlhttp = new XMLHttpRequest();
			} else {
				try {
					xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
				} catch (e) {
					try {
						xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
					} catch (e) {
						xmlhttp = false;
					}
				}
			}
		})();
	}
	return xmlhttp;
}

// nodes
var name = document.getElementById("name");
var email = document.getElementById("email");
var message = document.getElementById("message");

name.onkeyup = function() {
	if (name.value != "") {
		document.getElementById("errorName").style.display = "none";
	}
}

email.onkeyup = function() {
	if (email.value != "") {
		document.getElementById("errorEmail").style.display = "none";
	}
}

message.onkeyup = function() {
	if (message.value != "") {
		document.getElementById("errorMessage").style.display = "none";
	}
}


document.getElementById("submit").onclick = function() {
	
	// check formular
	if (name.value == "") {
		document.getElementById("errorName").style.display = "inline";
		name.focus();
		return;
	}
	
	if (email.value == "") {
		document.getElementById("errorEmail").style.display = "inline";
		email.focus();
		return;
	}
	
	if (message.value == "") {
		document.getElementById("errorMessage").style.display = "inline";
		message.focus();
		return;
	}
	
	// send formular
	params = "name="+encodeURIComponent(name.value) +
		"&email="+encodeURIComponent(email.value) +
		"&message="+encodeURIComponent(message.value);
	
	var request = new XHR();
	request.open("POST", "send.php");
	request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	request.setRequestHeader("Content-length", params.length);
	request.setRequestHeader("Connection", "close");
	request.onreadystatechange = function() {
		if (request.readyState == 4) {
			document.getElementById("sending").style.display = "none";
			document.getElementById("thankyou").style.display = "block";
		}
	}
	request.send(params);
	document.getElementById("submit").style.display = "none";
	document.getElementById("sending").style.display = "block";
}