Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/134c63f2e75f58d1f41724d6ff0e5357.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563