<script type="text/javascript">
    function Blocked() {
        // i chce aby w tym momencie pole tekstowe login zmienilo status na disabled
    }
</script>

<input type="text" name="login" value="" onClick="Blocked()" />

function Blocked(obj) {
        obj.disabled = true;
    }

<script type="text/javascript">
function Blocked() {
    var login  = document.getElementById('login');
    var pass   = document.getElementById('pass');
    var cpass  = document.getElementById('cpass');
    var email  = document.getElementById('email');
    var statut = document.getElementById('statut');
    var btn    = document.getElementById('btn');
    
    login.disabled = true;
}
</script>
        print 'asd
        
        <script type="text/javascript">
            Blocked();
            setTimeout("window.location = \''.$_site.'\';",5000);
        </script>';

<input type="text" name="login" value="" id="login" maxlength="30" onChange="vLogin()" />