Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4a0d80d8a4b7b5cd0b52dc7b6387a133.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563