on line 57 you have

$fp = fopen($file,"a");

change that to

$fp = fopen($file,"x");

and it should fix it! (I believe!)

I've changed but i get an error
Warning: fopen(guestbook.txt) [function.fopen]: failed to open stream: File exists in /home/...
Warning: fwrite(): supplied argument is not a valid stream resource in /home/...
Warning: fclose(): supplied argument is not a valid stream resource in /home/...

have you created the file?

I too very much need the last entry on top. I've set this up as a beta. And will try to add some security. E-mail validation, and perhaps a captcha, to avoid spam. Also I think separate pages when messages exceed , say 20, is something we must have. But I'd like to stop right about there, to keep it simple. Help very much appreciated. Thanks a lot to you coders.

Check http://www.php.net/manual/en/function.fopen.php

$fp = fopen($file,"c");

might work.

But not for me yet. :(