Headers already sent by (output started at /pathtotheme/functions.php:6)

If you get the following error when making changes to your wordpress theme, there’s a good chance you’ve got whitespace in your functions.php file.

“Warning: Cannot modify header information – headers already sent by (output started at /home/username/public_html/wp-content/themes/themename/functions.php:6) in /home/username/public_html/wp-includes/pluggable.php on line 390″

The number after “functions.php:” indicates the line in the file which is faulty, if you have empty lines at the end of the file, remove them and you should be back up and running.