function vLogin()
{
var vlogin = document.getElementById('vlogin');
var login  = document.register.login;


if(login.value.length >= 6)
{
advAJAX.get({
    url: "modules/account/validate.php?login="+login.value,
    onSuccess : function(obj) {var a; a = obj.responseText; if(a == 1) {vlogin.innerHTML = "prawda";}  if(a == 0) {vlogin.innerHTML = "falsz";}},
    onError : function(obj) {alert("Error: " + obj.status);},
});


}
else
{
vlogin.innerHTML = " <img src='img/icons/_00.png'> <font face='Verdana size='1' color='red'>Zbyt krótki login</font>";
}
}

if(isset($_GET['login']))
{
$login = $_GET['login'];


$query="SELECT * FROM `user` WHERE `login`='$login'";
$sql=mysql_query($query);

if($rows=mysql_fetch_array($sql))
{
print "0";
}
else
{
print "1";
}
}

<script>
function vLogin()
{
var vlogin = document.getElementById('vlogin');
var login  = document.register.login;


if(login.value.length >= 6)
{
advAJAX.get({
    url: "modules/account/validate.php?login="+login.value,
    onSuccess : function(obj) {var a; a = parseInt(obj.responseText); if(a == 1) {vlogin.innerHTML = "prawda";} else {vlogin.innerHTML = "falsz";}},
    onError : function(obj) {alert("Error: " + obj.status);},
});
}
else
{
v1 = 0;
vlogin.innerHTML = " <img src='img/icons/_00.png'> <font face='Verdana size='1' color='red'>Zbyt krótki login</font>";
}
}
</script>


<form name='register' method='POST' action='' onSubmit='return Validate()'>


Login: <input type='text' name='login' value='' style='width:180px;' maxlength='30' onChange='vLogin()'>
<span id='vlogin'></span>

</form>

if(isset($_GET['login']))
{
$login = $_GET['login'];


$query="SELECT * FROM `user` WHERE `login`='$login'";
$sql=mysql_query($query);

if($rows=mysql_fetch_array($sql))
{
print "0";
}
else
{
print "1";
}
}