SQL语句不返回任何内容

我有一个表单，要求用户在继续操作之前回答自己的安全问题。我的表格如下：

    <form action="securitychecked.php" method="post">
<table width="70%" border="0">
  <tr>
    <td><?php $result = mysql_query("SELECT secret_question FROM public WHERE active = 'activated' AND ni = '". $_SESSION['ni']."'")
or die(mysql_error()); 
if (mysql_num_rows($result) == 0) {
       echo '<hr><h4>This Person Has Not Setup A Security Question</h4><hr> ';
    } else {
while($info = mysql_fetch_array($result))
{
        echo  $info['secret_question'];
}
    }?></td>
    <td><span id="sprytextfield1">
      <input type="text" name="secret_answer" id="secret_answer" />
      <span class="textfieldRequiredMsg">*</span></span></td>
  </tr>
  <tr>
    <td>&nbsp;</td>
    <td><br /><input name="" type="submit" value="Continue" /></td>
  </tr>
</table>
</form>

我的php代码如下：

    <?php
$secret_anwser=$_POST['secret_anwser'];
$secret_anwser = stripslashes($secret_anwser);
$secret_anwser = mysql_real_escape_string($secret_anwser);
$sql="SELECT secret_anwser FROM public WHERE secret_anwser ='$secret_anwser' AND active = 'activated' AND ni = '". $_SESSION['ni']."'";
$result=mysql_query($sql);
// Mysql_num_row is counting table row
$count=mysql_num_rows($result);

if($count==1){
header("location:votenow.php");
}
?>

我有一个叫public的表和一个叫secret_anser的字段，但即使输入了正确的值，我仍然会得到一个空白页。有人能帮我吗？

感谢