Very simple. The form emitted by the password-protected post (in place of the content) does not meet basic WAI guidelines (label associated with form element using the for= attribute). Normally, I would rewrite this myself, but this is generated by the core (get_the_password_form in post-template.php).
If there is a simple workaround or overload, that would be great. I will be trying to figure out if I can overload it, but it does not appear to be be possible.
This isn't actually an easy issue to address, as the label's for attribute needs a unique ID, so I am applying the following hack:
function get_the_password_form() {
$id = "password_".get_the_ID();
$output = '<form action="' . get_option('siteurl') . '/wp-pass.php" method="post">
<p>' . __("This post is password protected. To view it please enter your password below:") . '</p>
<p><label for="'.__($id).'">' . __("Password:") . ' <input name="post_password" id="'.__($id).'" type="password" size="20" /></label> <input type="submit" name="Submit" value="' . __("Submit") . '" /></p>
</form>
';
return $output;
}
