note 36772 added to function.header

Why does my locaL Dev Server (Win2000, Apache 2.x, PHP 4.x, MySQL 4.x) - Set to display ALL Notices, Warning & Errors in the php.ini.. (So force my hand in writting better PHP code) - not seem to allow the use of the header() fuunction. While trying to do a page session variable (username / passwork) check - and if absent re-direct to login page with the use of "header(Location:thatloginpage.php)" The page output when viewed throgh browser / apache running on dev server - i get: "Warning: Cannot modify header information - headers already sent by (output started at c:\\www\mypage\admin_area\index.php:1) in c:\www\mypage\admin_area\index.php on line 3" Line three is out of interest the header(Location:thatloginpage.php) just out of interest any help apreciated - Julian ---- Manual Page -- http://www.php.net/manual/en/function.header.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+36772 Delete -- http://master.php.net/manage/user-notes.php?action=delete+36772&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+36772&report=yes Search -- http://master.php.net/manage/user-notes.php