Cannot send session cache limiter, what am i missing?

can someone please tell me what Im missing? this simple script

<?
session_start();
?>

displays the fol开发者_JAVA技巧lowing error message:

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at C:\xampp\htdocs\test3\index.php:1) in C:\xampp\htdocs\test3\index.php on line 2

thanks.

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It may be a Byte Order Mark generated by your text editor.

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Check if there are any whitespaces before <? If there is any output before session_start() - it will not work

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session_start(); should be the first thing on your page. Before any text, or spaces. Nothing should precede it in your page.

<?php

  session_start();

  /* code here */

?>