Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0fbb3c6c8a039a89e400ab0aeeb3a70d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563