Fb:captcha
From Facebook Developers Wiki
[edit] Description
Renders a CAPTCHA on your canvas page inside of a form. When that form is submitted to a canvas page, your callback URL will be called with the additional POST parameter fb_sig_captcha_grade=1 to indicate a successfully completed CAPTCHA.
[edit] Attributes
| Required | Name | Type | Description | |
| optional | showalways | bool | When showalways is set, Facebook will show a CAPTCHA to all users. If it is not set, then only users with accounts unverified by Facebook will see the CAPTCHA. This is the same logic Facebook uses for determining whether to show CAPTCHAs. (Default value is false.) |
|---|
[edit] Examples
<form action="index.php" method="post">
<fb:captcha showalways="true" />
<input type="submit" />
</form>
 |
