odeslání dat metodou POST přes JS

<script type="text/javascript">
function login_user()
{
var nick=window.document.login.nick.value;
var pass=window.document.login.pass.value;
var to_send= "nick=" + nick + "&pass=" + pass;
var pozadavek=null;
if (window.XMLHttpRequest) {pozadavek=new XMLHttpRequest();}
else if (window.ActiveXObject) {pozadavek=new ActiveXObject("Microsoft.XMLHTTP");}
else {alert("Update please your browser");}
if (pozadavek)
    {
    pozadavek.onreadystatechange=function ()
        {
        if (pozadavek.readyState ==4)
            {
            var vysledek=pozadavek.responseText;
            window.document.getElementById("content").innerHTML=vysledek;
            }
        }
    pozadavek.open("POST", "login.php", true);
    pozadavek.setRequestHeader("Conent-Type","application/x-www-form-urlencoded; charset=iso-8859-2");
    pozadavek.send(to_send);
    }
}
</script>
<form name="login">
<input type="text" size="25" name="nick">
<input type="password" size="25" name="pass">
<input type="button" value="Odeslani" onClick="login_user();">
</form>

<?php
$nick = $_REQUEST["nick"];
$password = $_REQUEST["pass"];
$vystup= $nick . "-" . $password;
echo $vystup;
?>

Notice: Undefined index: nick in F:\softwear\xampp\htdocs\stranky\login.php on line 2
Notice: Undefined index: pass in F:\softwear\xampp\htdocs\stranky\login.php on line 3