From this page https://gist.github.com/BronsonQuick/2366001
I tried applying this, but it doesn't work.
Please advice. Thanks
//This is a filter to change the default validation message that Gravity Forms generates
add_filter('gform_validation_message', 'change_validation_message', 10, 2);
function change_validation_message($message, $form)
return "<div class='validation_error'>Oops! Looks like there’s something wrong. Please review the form above.</div>";