My website worked perfectly.
But then I upgraded my vps with x-cache, mysql 5.5, and also
.htaccess cache time
# 1 MONTHS
Header set Cache-Control "max-age=2419200, public"
ExpiresDefault "access plus 1 month"
Header set Cache-Control "max-age=604800, public"
ExpiresDefault "access plus 1 week"
The website still works perfectly but when I log with admin account, and access admin panel I get this error
Warning: Cannot modify header information - headers already sent by (output started at /home/xxxxxxx/public_html/qa-include/qa-theme-base.php:1) in /home/xxxx/public_html/qa-include/qa-page.php on line 329
The error disappears if i click on other page rather than admin panel.
it seems that it already gets a header when i click admin panel but where?
I restarted the vps but the error is still there
And I also tried to remove all the sessions in /tmp