You're almost there. The correct URL is http://site.n.ml.org/info/t1lib/. Directory requests in HTTP must always be terminated with a slash for practical reasons: If your web browser thought it was at the URL http://www.example.net/info, then relative links would be resolved based on the directory that "document" (info) was in, http://www.example.net/. Historically, web servers such as Apache have issued a "redirect" message when it was detected that a request was for a directory without the terminating slash, so visiting http://www.example.net/info would result in being redirected to http://www.example.net/info/. This allows the index.html in http://www.example.net/info/ to specify relative links such as <a href="about.html">About Us</a>, which would take you to http://www.example.net/info/about.html (whereas if your browser thought you were at http://www.example.net/info, without the slash, then going to "about.html" would take you to http://www.example.net/about.html).
However, the W3C now encourages URL maintainers to use "typeless" URLs whenever possible, so URLs such as http://www.example.net/info/about.html might become http://www.example.net/info/about. This is made possible with Apache's MultiViews option, and needs no specific configuration. With typeless URLs, though, a request for http://site.n.ml.org/info/t1lib could mean http://site.n.ml.org/info/t1lib/, or it could mean http://site.n.ml.org/info/t1lib.html, with no way for Apache to determine which you mean.
The gist of this is that web servers that transparently redirect you to the "correct" URL (with a slash at the end) may start to disappear as more sites move to typeless URLs. Specifically, this one already has, so please update your bookmarks to include the trailing slash.