head.php와 head.sub.php문제

제가 아무생각없이 head.php에 베너를 한개 추가했는데(메모장에서 작업했습니다.)
메인화면에 다음과 같은 경고가 뜹니다.

Warning: Cannot modify header information - headers already sent by (output started at /home/hosting_users/ghh_allsmiles/www/bbs/head.php:1) in /home/hosting_users/ghh_allsmiles/www/bbs/head.sub.php on line 25

Warning: Cannot modify header information - headers already sent by (output started at /home/hosting_users/ghh_allsmiles/www/bbs/head.php:1) in /home/hosting_users/ghh_allsmiles/www/bbs/head.sub.php on line 27

Warning: Cannot modify header information - headers already sent by (output started at /home/hosting_users/ghh_allsmiles/www/bbs/head.php:1) in /home/hosting_users/ghh_allsmiles/www/bbs/head.sub.php on line 28

Warning: Cannot modify header information - headers already sent by (output started at /home/hosting_users/ghh_allsmiles/www/bbs/head.php:1) in /home/hosting_users/ghh_allsmiles/www/bbs/head.sub.php on line 29

Warning: Cannot modify header information - headers already sent by (output started at /home/hosting_users/ghh_allsmiles/www/bbs/head.php:1) in /home/hosting_users/ghh_allsmiles/www/bbs/head.sub.php on line 30

Warning: Cannot modify header information - headers already sent by (output started at /home/hosting_users/ghh_allsmiles/www/bbs/head.php:1) in /home/hosting_users/ghh_allsmiles/www/bbs/head.sub.php on line 31

head.sub.php파일의 25~31 라인의 내용은

25 : header("Content-Type: text/html; charset=$g4[charset]");
26 : $gmnow = gmdate("D, d M Y H:i:s") . " GMT";
27 : header("Expires: 0"); // rfc2616 - Section 14.21
28 : header("Last-Modified: " . $gmnow);
29 : header("Cache-Control: no-store, no-cache, must-revalidate"); // HTTP/1.1
30 : header("Cache-Control: pre-check=0, post-check=0, max-age=0"); // HTTP/1.1
31 : header("Pragma: no-cache"); // HTTP/1.0

입니다.

현재는 25~31번 라인을 주석처리 해놨으나
메인화면에서 로고의 위치, 상단메뉴의 위치등이 원래자리에서 밑으로 처진 상태입니다.
근본적인 해결책이 필요합니다...도와주세요 ㅠㅠ

ps. 27번 라인은 무슨뜻인지도 궁금합니다...