The guys have really given you good answers already. Personally I like .ini files outside your document root. Also make sure (if you're on a linux hosting env) that your file is only readable by your web server and not writable.
You can then simply parse the INI file and use your configuration settings like that. (this is if you're using a language such as PHP or so, JavaScript ect won't work here.)
But it's like they said. It all depends on what data you want to have in your config file and what you want todo with it.
Regards
Conrad c'',)
