Where would I find where an .htaccess file is located and being used on a Mac OS X Lion server that sets Basic Auth on an Apache server? I've installed some software, namely, a continuous integration (CI) server (Jenkins) on a Mac Mini running Lion Server. The server, by default, runs from port 8080 on local host via the url: http://localhost:8080. However, when I try to access the page it seems to be protected by Basic Auth and it asks me for a name and a password. 

Granted, I never set that Basic Auth and I've been told I can remove the authentication and use that port for the CI server. However, I'm hard pressed to find an .htaccess file anywhere that sets the Basic Auth? If it's not set in an .htaccess file then where would Basic Auth be set?
You might try looking in /etc/apache2/sites/
That was the directory in 10.6; in 10.5, it was /etc/httpd/sites

On 10.5 and 10.6 server, the server app can be used to set access restrictions, and that is the location where the config files are written.

If your web setup is not complicated, the filename may be similar to 0000_any_8080_(HOST).conf