Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/753b2a017c29a4d47b672480c4c85b57.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563