Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/26bb4bf5b5b3926605a8b92d6bf5c60f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563