SELinux has its own system of granting access. Your process ever has to be granted to access files on filesystem depending on SELinux context. There are some default politics and contexts defined in SELinux those are usefull for default cases of your installation. Just web files are expected to be in '/var/www'. You can mostly check the current context of files or processes using switch '-Z', see
[root@localhost]# ls -Z /var
drwxr-xr-x. root root system_u:object_r:httpd_sys_content_t:s0 www
Check the context of /srv/mysite
[root@localhost]# ls -Z /srv
drwxr-xr-x. root root system_u:object_r:var_t:s0 mysite
The Apache HTTPD server is allowed to access files with SELinux type httpd_sys_content_t byt it is NOT allowed to access files with SELinux type var_t.
1. Change the SELinux type for your directory and check the context
[root@localhost]# chcon -R -t httpd_sys_content_t /srv/mysite
[root@localhost]# ls -Z /srv
drwxr-xr-x. root root unconfined_u:object_r:httpd_sys_content_t:s0 mysite
Check if your webiste is working right now.
Till now it is not finished yet, while you relabel filesystem to default or if you use a daemon to check or relabel itself, you risk to lose your new labeling.
2. Make the default labaling for your directory
Create the default labeling by 'semange' and apply it on your directory by 'restorecon'
[root@localhost]# semanage fcontext -a -t httpd_sys_content_t /srv/mysite
[root@localhost]# restorecon -v -R /srv/mysite
[root@localhost]# ls -Z /srv
drwxr-xr-x. root root unconfined_u:object_r:httpd_sys_content_t:s0 mysite
Right now your SELinux labeling is fixed.
Note: It is possible regular expressions to define default context.
Debian: I'm not a Debian user, so the SELinux type can be a bit different, the principle is just the same, check the SELinux type of your apache directory and set it on your directory you want to be accessible from apache.
Fedora SELinux documentation: http://docs.fedoraproject.org/en-US/Fedora/13/html/Security-Enhanced_Linux/