when i try to sign-up i got this message: Warning: Cannot

Hello,
when i try to sign-up i got this message:
Warning: Cannot modify header information - headers already sent by (output started at /home/lapsiho/public_html/wp-content/themes/default/header.php:2) in /home/lapsiho/public_html/wp-includes/pluggable.php on line 876

Website: http://www.la-psiholog.com