Maybe. It depends on what modules are loaded on your web server. Your options will range from keeping a simple list of users in a flat file, to keeping them in a database and customizing the queries.
http://httpd.apache.org/docs/2.2/howto/auth.html
Another option - just brainstorming here - is to use something like mod_rewrite to redirect the calls to the physical file to something like a PHP script that can manage the user/password authentication for your, and if authenticated, go out and load the html file that was requested. So calls to www.some.com/10203.html
actually get directed to www.some.com/auth.php?10203.html
, which would control access to that underlying html file. That would of course require mod_rewrite to be installed, which is pretty common even for shared hosting environments.