login.html

 <?php
/*************************************/
session_start();
$digit = "6";

function generate_code($digit) {
    $random_it="";
    $letters = "abcdefghjkmnprstuxvyz23456789ABCDEFGHJKMNPRSTUXVYZ";
    for ($i=0; $i<$digit; $i++) {
        $salla .= $letters{rand(0,strlen($letters)-1)}; 
    }
    return $salla; 
}
$security_code = generate_code($digit);
$_SESSION['security_code'] = $security_code;
/*************************************/
?>

   <center>
        <table class="login">
            <tr>
                <td>
                    <table>
                        <tr>
                            <td style="padding: 0 10px 0 42px; height: 280px; width: 170px;">
                                <a href="/"><img border=0 src="/images/vesta_logo.png" alt="Vesta Control Panel" style="margin: 0 0 0 0;" /></a>
                            </td>
                            <td style="padding: 20px 0 0 0;">
                                <form method="post" action="/login/" >
                                <table class="login-box">
                                    <tr>
                                        <td syle="padding: 12px 0 0 2px;">
                                            <?php print __('Username');?>
                                        </td>
                                    </tr>
                                    <tr>
                                        <td>
                                            <input tabindex="1" type="text" size="20px" style="width:240px;" name="user" class="vst-input">
                                        </td>
                                    </tr>
                                    <tr>
                                        <td style="padding: 12px 0 0 2px;">
                                            <?php print __('Password');?>
                                            <span style="padding:0 0 0 14px;">
                                                <a tabindex="5" class="vst-advanced" href="/reset/">
                                                    <?php print __('forgot password');?>
                                                </a>
                                            </span>
                                        </td>
                                    </tr>
                                    <tr>
                                        <td>
                                            <input tabindex="2" type="password" size="20px"  style="width:240px;" name="password" class="vst-input">
                                        </td>
                                    </tr>

                                      <tr>
                                        <td height="20px">
                                        </td>
                                    </tr>

                                     <tr>
                                        <td>
                                        <div>Security Code : <label style="color: #aaa;"><?php echo  $security_code;?></label></div>
                                           <input type="text" tabindex="2" name="security_code" class="vst-input" style="width:240px;"/>
                                        </td>
                                    </tr>

                                    <tr>
                                        <td height="28px">
                                        </td>
                                    </tr>
                                    <tr>
                                        <td style="padding: 0 0 12px 0;">
                                            <input tabindex="3" type="submit" value="<?php print __('Log in');?>" class="button">
                                        </td>
                                    </tr>
                                </table>
                            </form>
                        </td>
                    </tr>
                    <tr>
                        <td colspan=2>
                            <div class="login-bottom">
                                <div style="height:20px"><?php if (isset($ERROR)) echo $ERROR ?></div>
                                <a class="vestacp" href="http://vestacp.com" >vestacp.com</a>
                            </div>
                        </td>
                    </tr>
                </table>
            </tr>
        </table>
    </center>
</body>

Is this the security question ?