Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2014c0cb69d989cc5c61a17d4814cb6e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563