.htaccess (Apache: The Definitive Guide, 3rd Edition)

3.7. .htaccess

An alternative to restarting to change Config files is to use the .htaccess mechanism, which is explained in Chapter 5. In effect, the changeable parts of the Config file are stored in a secondary file kept in .../htdocs. Unlike the Config file, which is read by Apache at startup, this file is read at each access. The advantage is flexibility, because the webmaster can edit it whenever he likes without interrupting the server. The disadvantage is a fairly serious degradation in performance, because the file has to be laboriously parsed to serve each request. The webmaster can limit what people do in their .htaccess files with the AllowOverride directive.

He may also want to prevent clients seeing the .htaccess files themselves. This can be achieved by including these lines in the Config file:

<Files .htaccess>
order allow,deny
deny from all
</Files>