The virtual host configurations should normally go in main Apache configuration file httpd.conf
. In the article link you posted above the configuration
creates a virtual host for user invision on domains n1.invision-web.net and www.invision-web.net
. Unless you have multiple site users which require configuration at a per-user level, this is not necessary. The article does not make this clear at all.
user.conf
is for per-user configuration. For example, where sites have multiple users (e.g. access to http://www.mysite.com/~pedro (delivering content from the home directory or sub-directory of user pedro) can be configured in the users.conf file. More details in Apache docs.