weird warning message when I go to www. [NSFW]

I get this message when I try to access my blog at http://www.sequoiaredd.com/blog instead of http://sequoiaredd.com/blog (NSFW!)

Warning: Cannot modify header information – headers already sent by (output started at /home/content/s/e/q/sequoiaredd87/html/blog/wp-content/themes/atahualpa333/functions/bfa_hor_cats.php:53) in /home/content/s/e/q/sequoiaredd87/html/blog/wp-includes/pluggable.php on line 865