What is the Error: Cannot modify header information… in WordPress?

Warning: Cannot modify header information – headers already sent by (output started at {PATH TO FUNCTIONS}:92) in /home/content/17/9436817/html/wp-includes/pluggable.php on line 881

If you’re seeing this error when publishing your post on WordPress it is probably because you’ve got some whitespace before or after your PHP tags.  Check before and after to be sure there are no extra lines or spaces and re-upload your files.