How to detect if there's no Gravatar and pust a custom message under Gravatar??

Have you read https://en.gravatar.com/site/implement/images/ ? It may help you using a hash and the d parameter to pull in a default image that has directions?

@ipstenu I would like to have my default gravatars untouched, I mean, with no directions and that kind of stuff. It would look nicer if I had a message under the picture.

You can use the API to pull your own default. That said, I want to say you should be able to parse the output to customize an ‘error’ as well, but you’ll want to study on the API.

have you read: https://codex.www.ads-software.com/Using_Gravatars
There is a function in there to check if there is an avatar:

function validate_gravatar($email) {
	// Craft a potential url and test its headers
	$hash = md5($email);
	$uri = 'https://www.gravatar.com/avatar/' . $hash . '?d=404';
	$headers = @get_headers($uri);
	if (!preg_match("|200|", $headers[0])) {
		$has_valid_avatar = FALSE;
	} else {
		$has_valid_avatar = TRUE;
	}
	return $has_valid_avatar;
}

Ok. I have copied the function above in my functions.php (thanks keesiemeijer) and here’s how I tried to validate and display a link for those who don’t have a Gravatar account while displaying my Default Gravatars:

<?php if(function_exists('get_avatar')) {
 echo get_avatar($comment, '80');
}
  if(function_exists('validate_gravatar')) {
  echo '<div style="margin-left: 20px;">
         <a href="myblogurl/miniturorial" title="How">(How?)</a>
         </div>';
} ?>

Except that it shows this custom link to all the users, both those who HAVE GRAVATARS and those WHO HAVEN’T.

What else am I supposed to do display the link under the users who DON’T have a Gravatar account?

if you are in a comment loop like this :
<?php foreach ($comments as $comment) : ?>
You can check if the commenter has a valid gravatar like this:

<?php
if(validate_gravatar($comment->comment_author_email)){
// has a valid gravatar
} else {
// has no gravatar
}
?>

FYI, the reason yours didn’t work is becuase you did this:

if(function_exists('validate_gravatar')) {
  echo '<div style="margin-left: 20px;">
         <a href="myblogurl/miniturorial" title="How">(How?)</a>
         </div>';

That just says ‘If the function ‘validate_gravatar’ exists, then show ‘How to?” Which isn’t what you wanted ??

Got it. Here’s the final code:

<?php if(function_exists('get_avatar')) {
   if(validate_gravatar($comment->comment_author_email)){
        echo get_avatar($comment, '80');
   }
   else {
        echo get_avatar($comment, '80');
        echo '<div style="margin-left: 20px;">
         <a href="https://yourblog/minitutorial" title="How">(How?)</a> </div>';
        }
}
?>

Thanks a lot, guys. Really appreciate your efforts. Thank you so much.