HowTo : Drupal, Headers already sent

Hi,

Simple as hell but very hard to track.
Here is one of the things that can drive you mad with Drupal 6.
I've just tracked one of the causes for the "headers already sent" message.

The directive is simple : Look if you have changed a module file and changed its encoding.
Sometimes you can't notice what you've done wrong, but this time, I did change the encoding of a module file, from ANSI to UTF-8.

Back to ANSI, no more error.