As I want to add a forum entry I got Apache's 500 server internel error. i tried to change .htaccess, php-conf etec but no success.
Error was: [warn] [client 22.214.171.124] mod_fcgid: HTTP request length 137744 (so far) exceeds MaxRequestLen (131072), referer: http://example.com/node/add/forum/1
After a research check error-logs of virtual host I found that /etc/apache2/mods-available/fcgid.conf must be changed.
I added following directive: