WordPress Header Error, Can't log in

Hello. I’ve got some serious problems with wordpress and I don’t even know why. I tried to log-in, but it pops me this error :

Warning: Cannot modify header information – headers already sent by (output started at /home/borut1/public_html/crizual.com/wordpress/wp-config.php:1) in /home/borut1/public_html/crizual.com/wordpress/wp-includes/pluggable.php on line 875

What should I do?

Thanks for helping me.