Error Message

When I post, I get an error message (see below). Even though I get this message, the post does seem to go to Facebook ok, but it has some miscellaneous characters at the very beginning of the post description.

Warning: Cannot modify header information – headers already sent by (output started at /home/content/57/9128057/html/wp-content/plugins/wordpress-simple-survey/output_quiz.php:28) in /home/content/57/9128057/html/wp-includes/pluggable.php on line 881

http://wordpress.org/extend/plugins/facebook/