this is my code:
<script type="text/javascript">
var RecaptchaOptions = {
theme : 'clean',
custom_theme_widget: 'recaptcha_widget'
};
</script>
<!--catcha code-->
<form action="mail2.php" method="POST" enctype="multipart/form-data">
<p style="font-size:0.8em;">Your Name*:</p>
<input type="text" name="from" value="" style="width:381px; height:
20px;" /><br /><br>
<p style="font-size:0.8em;">Your Email*:</p><input type="text"
name="mailadd" value="" style="width:381px; height:20px;" /><br /><br>
<p style="font-size:0.8em;">Subject:</p><input type="text"
name="subject" value="" style="width:381px; height:20px;" /><br /><br>
<p style="font-size:0.8em;">Your address*:</p><input type="text"
name="addr" value="" style="width:381px; height:20px;" /><br /><br>
<p style="font-size:0.8em;">Your address(cont):</p><input type="text"
name="addrr" value="" style="width:381px; height:20px;" /><br /><br>
<p style="font-size:0.8em;">City*:</p><input type="text" name="city"
value="" style="width:381px; height:20px;" /><br /><br>
<p style="font-size:0.8em;">State*:</p><input type="text" name="state"
value="" style="width:381px; height:20px;" /><br /><br>
<p style="font-size:0.8em;">Zip Code:</p><input type="text"
name="zipc" value="" style="width:381px; height:20px;" /><br /><br /
><br>
<p>Message:<br />
<textarea cols="47" rows="10" name="message"></textarea></p><br />
<p style="font-size:0.8em;">Attach Your Photo:</p><input type="file"
name="fileatt" /><br /><br />
<?php
require_once('recaptchalib.php');
$publickey = "6Ldjy9ASAAAAAK8j5EddDwBGkB7KplCl9GmMm0Ti"; //
you got this from the signup page
echo recaptcha_get_html($publickey);
?>
<!--catcha code-->
<div id="recaptcha_widget" style="display:none">
<div id="recaptcha_image"></div>
<div class="recaptcha_only_if_incorrect_sol"
style="color:red">Incorrect please try again</div>
<span class="recaptcha_only_if_image">Enter the words above:</span>
<span class="recaptcha_only_if_audio">Enter the numbers you hear:</
span>
<input type="text" id="recaptcha_response_field"
name="recaptcha_response_field" />
<div><a href="javascript:Recaptcha.reload()">Get another CAPTCHA</
a></div>
<div class="recaptcha_only_if_image"><a
href="javascript:Recaptcha.switch_type('audio')">Get an audio CAPTCHA</
a></div>
<div class="recaptcha_only_if_audio"><a
href="javascript:Recaptcha.switch_type('image')">Get an image CAPTCHA</
a></div>
<div><a href="javascript:Recaptcha.showhelp()">Help</a></div>
</div>
<script type="text/javascript"
src="
http://www.google.com/recaptcha/api/challenge?
k=6Ldjy9ASAAAAAK8j5EddDwBGkB7KplCl9GmMm0Ti">
</script>
<noscript>
<iframe src="
http://www.google.com/recaptcha/api/noscript?
k=6Ldjy9ASAAAAAK8j5EddDwBGkB7KplCl9GmMm0Ti"
height="300" width="500" frameborder="0"></iframe><br>
<textarea name="recaptcha_challenge_field" rows="3" cols="40">
</textarea>
<input type="hidden" name="recaptcha_response_field"
value="manual_challenge">
</noscript>
<!--catcha code-->
<p><input type="submit" value="Send Email" /></p>
</form>
please guide me where is error? why my captcha response field is empty?