OOPS! (website error message)

I am getting the following error msg when I try to go to my site

Warning: Cannot modify header information – headers already sent by (output started at /home/content/65/4840465/html/wp-content/themes/vita.1.6/vita/functions.php:246) in /home/content/65/4840465/html/wp-includes/pluggable.php on line 865

It is because I tried editing the function file, I think. Last time, it went back to normal after a day or so but I don’t know if that was natural or if somebody had to fix this problem. Please provide assisstance. Thank you.

http://www.big-nasty.com