You have an error in your SQL syntax

<?php
include "./connect.php";// připojení k databázi

if(isset($_POST['submit'])) {

  $nick = mysql_real_escape_string($_POST['nick']);
  $IP = mysql_real_escape_string($_POST['IP']);
                                                
  /* --- KONTROLA ZADANÝCH ÚDAJŮ --- */   
  if($nick==""){
    echo'Nebyl vyplněn nick!';
  }
  else if($IP==""){
    echo'Nebylo vyplněno IP';
  }
  else{
    $sql= mysql_query("INSERT INTO zond VALUES ('','$nick',','$IP')") or die(mysql_error());
    echo'Zond byl přidán!';
  }
}
?>

<form action="#" method="post">     
  <table>
    <tr>
      <td>Nick: </td>
      <td><input type="text" name="nick" value="<?php if(isset($_POST["nick"])){echo $_POST["nick"];}?>" size="25" tabindex="1" /></td>
    </tr>
    <tr>
      <td>Ip: </td>
      <td><input type="text" name="IP" value="<?php if(isset($_POST["IP"])){echo $_POST["IP"];}?>" size="25" tabindex="4" /></td>
    </tr>
    <tr>
      <td colspan="2"><input type="submit" name="submit" value="Odeslat" /></td>
    </tr>
  </table>
  </center>
</form>

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'wwwww')' at line 1