If you're using Red Hat Enterprise Linux (RHEL) or one of it's variants (CentOS, etc.), you may have noticed that using a non-standard document root for your Apache-based web site results in a DocumentRoot does not exist warning if the directory exists. The most likely cause of this problem is SELinux.

The fix for the problem is to change the security context of your new DocumentRoot to match that of the system's original document root. Here's how:

$ ls -la --context /var/www/html
drwxr-xr-x  root root system_u:object_r:httpd_sys_content_t .
$ chcon -R system_u:object_r:httpd_sys_content_t /new/docroot

Obviously, /new/docroot in the example above should be the path to your document root.