Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/481602ec656fb0a6e0a04e4dcc318ac3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563