What does a dot mean in a URL path?

In a question regarding a jQuery Ajax problem, the asker was trying to use a . in the beginning of a relative URL. I advised him to remove it, but have no idea what a dot actually does there.

His relative URL looked like this:

./delete-misc/test-ajax-code.php

I tried looking in the RFCs, without success. I know what the dot does in command line (either Linux or Win), it represents the current directory.

I'd like to know: how does this work on the Internet in a URL? Does it have any best-practice uses? Detailed explanations are most welcome.