headers..

<?php

ob_start();

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

   $username=trim($_POST['username']);

   $password=$_POST['password'];

   $password2=$_POST['password2'];

   $email_address=trim($_POST['email_address']);

   $age=$_POST['age'];

   $sex=$_POST['sex'];

   $country=$_POST['country'];

   $sign_date=date("d.m.Y H:i");

    if((empty($username)) or (empty($password)) or (empty($password2)) or (strpos($email_address, "@") === false) or (strpos($email_address, ".") === false)){

         header("location: index.php?Alert=0");

    }else{

         require('db.php');

         $PocetStejnych=MySQL_Result(MySQL_Query("SELECT COUNT(*) FROM `uzivatele` WHERE `username`='$username' OR `email_address`='$email_address'"),0);

    if($PocetStejnych!=0){

         header("location: index.php?Alert=1");

    }elseif($password!=$password2){

         header("location: index.php?Alert=2");

    }else{

         $passwordmd5=md5($password2);

         $VlozData=MySQL_Query("INSERT INTO uzivatele VALUES ('', '$username', '$passwordmd5', '$email_address', '$age', '$sex', '$country', '0', '', '$sign_date', '', '')") or die (MySQL_Error());

         header("location: index.php?Alert=3");

    }

  }

}else{

         header("location: index.php?Alert=4");

}

ob_end_flush();

?>