Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0474a7415e2a7e6c303a8348b0fd7f53.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563