At checkout users get error Warning: Cannot modify header

hi everyone,

at checkout i get this error

Warning: Cannot modify header information - headers already sent by (output started at /home/alati/public_html/catalog/language/srb/payment/bank_transfer.php:1) in /home/alati/public_html/system/engine/controller.php on line 27

the store worked properly but now this happened. any help wold be appreciated.

check the top of the file /home/alati/public_html/catalog/language/srb/payment/bank_transfer.php. Most likely there's some whitespace at the top of the file.