note 69686 added to function.header

When i use header to redirect to another page i am getting this error.. Warning: Cannot modify header information - headers already sent by (output started at /newsite/Login.php:16) in /newsite/Login.php on line 178 Can anyone say why this error comes? ---- Server IP: 203.16.234.19 Probable Submitter: 202.164.138.226 ---- Manual Page -- http://www.php.net/manual/en/function.header.php Edit -- https://master.php.net/note/edit/69686 Del: integrated -- https://master.php.net/note/delete/69686/integrated Del: useless -- https://master.php.net/note/delete/69686/useless Del: bad code -- https://master.php.net/note/delete/69686/bad+code Del: spam -- https://master.php.net/note/delete/69686/spam Del: non-english -- https://master.php.net/note/delete/69686/non-english Del: in docs -- https://master.php.net/note/delete/69686/in+docs Del: other reasons-- https://master.php.net/note/delete/69686 Reject -- https://master.php.net/note/reject/69686 Search -- https://master.php.net/manage/user-notes.php