user auth.. with mysql and cookies.. help

sorry, bother all of you with my same question i was learn to make user auth with mysql and using cookies, i have trouble with this error message; Warning: Cannot add header information - headers already sent by (output started at ../functions.inc:54) in ../functions.inc on line 49 Warning: Cannot add header information - headers already sent by (output started at ../functions.inc:54) in ../functions.inc on line 50 Warning: Cannot add header information - headers already sent by (output started at ../functions.inc:54) in ../functions.inc on line 51 Warning: Cannot add header information - headers already sent by (output started at ../functions.inc:54) in ../login.php on line 12 in this case i use 4 file .. 1)index.html -- sending data (methode post to login.php); 2)login.php 3)function.inc -- all the function i use 4)common.inc -- global variable; 2...login.php................. <?php require 'functions.inc'; deleteCookies(); if (authenticateUser($form_username, $form_password)) {

      setcookie("cookie_passwd", $form_password);
      setcookie("cookie_user", $form_username);
      header("Location:http://$http_host/$docroot/report.php");
      exit();

} else{ header("Location:http://$http_host/$docroot/error1.htm"); exit(); } 3.function.inc <? require 'common.inc'; function DisplayErrMsg($message) { printf ("<blockquote><blockquote><blockquote><h3><fontcolor=\"#cc0000\"> %s</font></h3></blockquote></blockquote></blockqoute>\n",$message); } function authenticateUser($user, $password) {

      global  $host, $httphost, $user_db, $password_db, $db, $docroot; 
      if (! ($link = mysql_pconnect($host, $user_db, $password_db)))
              { 
              DisplayErrMsg(sprintf("internal Error %d: %s \n", mysql_errno(), mysql_error() ));
              DisplayErrMsg(sprintf("internal Error %s %s %s %d: %s \n", $host, $user, $password, mysql_errno(), mysql_error() )); 
              return 0; 
      } 
      if (! ($result = mysql_db_query("$db","select * from user_login where userid = '$user'")))
              {
              DisplayErrMsg(sprintf("internal Error %d: %s \n", mysql_errno(), mysql_error() ));
              return 0 ; 
              } 

      if (($row = mysql_fetch_array($result)) && ($password==$row["password"] && $password != "")) 
              return 1; 
      else
              return 0; 
} 

function deleteCookies() {

      for ($i=0; $i<$total_items; $i++)
              {
              setcookie("items_tray[$i]","");
              setcookie("quantity[$i]","");
              }

setcookie("items_tray",""); setcookie("total_items",""); setcookie("quantity",""); } ?> and 4. common.inc <? $host = "localhost"; $user_db = "root"; $password_db = ""; $db = "master_report"; $http_host = "reymond.unri.ac.id/"; $docroot = "security"; ?> ~ could you tell me what and where is the mistake ... thank for all of you all kindness regards anton ------Linux is Power-------