2 Dec 31, 2007 11:40
It looks like your editor left some blank space (space, tab, new line) either before the first <?php or after the closing ?>
Use a plain text editor like Notepad or (better) Notepad++ or Crimson editor. There are hundreds of them around. Do not use an HTML editor when you edit php files.
If you have a backup from the _main.php file, you'd better start again. If you don´t you'll have to open the file, search and delete the whitespace.