Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d479e7f933e40b3a3e5f9e665aa3dc40.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563