Add captcha in contacts us page in magento

Replace this file to your /test/app/design/frontend/base/default/template/contacts/form.phtml

 
<script type="text/javascript">
function ram_mk()
{


a=document.getElementById('tot').value;
b=document.getElementById('catcha').value;
if(a!=b)
{
document.getElementById('mk_x').style.display='';
return false;
}
}

function akk()
{
ab=Math.floor((Math.random()*10)+1);
ab1=Math.floor((Math.random()*8)+1);
var tot=ab+ab1;
document.getElementById('captcha_1').innerHTML=ab;
document.getElementById('captcha_2').innerHTML=ab1;
document.getElementById('tot').value=tot;
document.getElementById('ab').value=ab;
document.getElementById('ab1').value=ab1;

}
window.onload = akk;
</script>
<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Academic Free License (AFL 3.0)
 * that is bundled with this package in the file LICENSE_AFL.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/afl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@magentocommerce.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magentocommerce.com for more information.
 *
 * @category    design
 * @package     base_default
 * @copyright   Copyright (c) 2012 Magento Inc. (http://www.magentocommerce.com)
 * @license     http://opensource.org/licenses/afl-3.0.php  Academic Free License (AFL 3.0)
 */
?>
<div class="middle_a">
<?php if($_REQUEST['msg']!='') { ?>
<ul class="messages"><li class="success-msg"><ul><li><span><?php echo $_REQUEST['msg']; ?></span></li></ul></li></ul>
<?php } ?>
<div class="contact_page">
    <h3><?php echo Mage::helper('contacts')->__('got questions?') ?></h3>
<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('contact-us')->toHtml() ?>
<div class="contact_form">
<form action="http://yourdomain.com/email.php" method="post">
<input type="hidden" name="url_x" value="<?php echo $currentUrl = Mage::helper('core/url')->getCurrentUrl() ?>" />

   <table width="100%" border="0" cellspacing="0" cellpadding="10">
<tr>
       
        <td><input name='name' type='text' class="text-df" onblur="if(this.value=='') this.value='Your Name'" onfocus="if(this.value=='Your Name') this.value=''" value="Your Name" required="required"/></td>
    </tr>
     <tr>
       
        <td><input name='email' type='email' class="text-df" onblur="if(this.value=='') this.value='Email Address'" onfocus="if(this.value=='Email Address') this.value=''" value="Email Address" required="required"/></td>
    </tr>
    <tr>
        <td><textarea name="Message" class="box-df1" required="required" onblur="if(this.value=='') this.value='Message'" onfocus="if(this.value=='Message') this.value=''" value="Message" >Message</textarea>
         </td>
    </tr>
     <tr>
       
        <td><input name="catcha" id="catcha" type='text' class="text-df" onblur="if(this.value=='') this.value='Enter Sum'" onfocus="if(this.value=='Enter Sum') this.value=''" value="Enter Sum" /></td>
    </tr>
    <tr style="display:none; color:#CC0000;" id="mk_x">
    <td align="center">Captcha not match</td>
    </tr>
   
    <tr>
       
        <td>
        <table width="100%">
        <tr>
        <td id="captcha-x">
        <span id="captcha_1">8</span> + <span id="captcha_2">5</span> = ?
       
        <input type="hidden" name="tot" id="tot" value="15"  size="2"/>
        <input type="hidden" name="ab" id="ab" value="15"  size="2"/>
        <input type="hidden" name="ab1" id="ab1" value="15"  size="2"/>
        </td>
        <td align="right">
        <input type='submit' name="submit" value="Send" class="send"  onclick="return ram_mk();" />
        </td>
        </tr>
        </table>
       
        </td>
    </tr>
</table>

</div>




<!-- contact_page -->

</div>

<!-- middle_a -->
<script type="text/javascript">
//<![CDATA[
    var contactForm = new VarienForm('contactForm', true);
//]]>
</script>


and add this file with name email.php to your magento root folder:

<?php
$catcha = $_REQUEST['catcha'];
$tot =$_REQUEST['tot'];
$ab = $_REQUEST['ab'];
$ab1 = $_REQUEST['ab1'];

$total=$ab+$ab1;
if($tot=='@100as_pti')
{
print("<script>window.location='".$_REQUEST['url_x']."'</script>");
exit;

}

if($catcha!=$total)
 {
print("<script>window.location='".$_REQUEST['url_x']."'</script>");
exit;

}



if($catcha==$total)
{

$mesg = $_REQUEST['Message'];
if(stristr($mesg, 'http') === FALSE)
{
if(stristr($mesg, 'https') === FALSE)
{

$_session['success']="Your inquiry was submitted and will be responded to as soon as possible. Thank you for contacting us";
$replymsg="Your inquiry was submitted and will be responded to as soon as possible. Thank you for contacting us";
$mail_to="shweta@ptiwebtech.com";
$sub="Contact us ";

$message = "<br>Name :  ".$_REQUEST['name'];
$message .= "<br>E-mail : ".$_REQUEST['email'];
$message .= "<br>Message  :  ".$_REQUEST['Message'];



$headers = "MIME-Version: 1.0" . "\r\n";
$headers .= "Content-type:text/html;charset=iso-8859-1" . "\r\n";
$headers .="From: ".$_REQUEST['email'];

mail($mail_to,$sub,$message,$headers);
}

 }

}

 print("<script>window.location='".$_REQUEST['url_x']."?msg=$replymsg'</script>");
 ?>


NOTE: replace $mail_to="shweta@ptiwebtech.com"; to your email id.