Warning: Cannot modify header information

I tried to add a new user through the registration signup page and got the following error at the top of the page

http://iawov.com
Warning: Cannot modify header information - headers already sent by (output started at /home/content/h/s/u/hsuso/html/wp-content/themes/bp-corporate/header.php:5) in /home/content/h/s/u/hsuso/html/wp-includes/pluggable.php on line 865

My website it http://www.iawov.com