Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/87f6df1840765d2ffa95e0385eed1bea.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563