function newsletter_submit(form)
{
    email = form.elements['email2'].value;
  	if (email.indexOf('@')==-1)
	{
		alert('Błędny adres e-mail');
		return false;
	}
	window.open('newsletter_submit.php?email='+email, '_blank', 'toolbar=0,scrollbars=0,location=0,statusbar=1,menubar=0,resizable=1,width=510,height=180,top=325,left=275');
	return false;
}

document.write(
'<form style="margin: 3px 0px 16px 0px" onsubmit="javascript:newsletter_submit(this)" action="#">'+
    '<input type="text" name="email2" style="width: 170" value="wpisz swój e-mail"/>'+
    '<input name="submit" type="submit" value="OK"/>'+
'</form>');