Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a5f6b0121e3b6b77f70288359694c239.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563