message error "Cannot modify header information"

flo34

my head and footer are in a folder called "fanal"
In the folder called "fanal" is also located a folder "collections" containing all zen album

here is the message I get on the top of the page when I go to the page "collections". maybe you could help me, as i'm absolutely not a developper...but a network engineer :

Warning: Cannot modify header information - headers already sent by (output started at /homez.14/fanallum/www/collections/zen/class-image.php:567) in /homez.14/fanallum/www/collections/index.php on line 9