Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /home/users1/l/likeday/domains/art.csfrags.ru/head.php:61) in /home/users1/l/likeday/domains/a rt.csfrags.ru/page/register.php on line 15

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/users1/l/likeday/domains/art.csfrags.ru/head.php:61) in /home/users1/l/likeday/domains/a rt.csfrags.ru/page/register.php on line 15

Выводит ошибку, в чем может быть проблема?
строчка 15