Automatic proxy configuration Rather than set a browser to always go via a particular proxy, automatic proxy configuration allows the service provider to settup a file of different proxies which the browser loads on start up and then uses to choose different proxies for making requests to different information providers. Remote access and authentication by Wally Grotophorst. Succinct explanation of the value of the proxy approach generally. The user is challenged for a username and password in a pop up box. If they answer correctly they have access to the directory for which the challenge was issued.
Mosaic tutorial explains how to set up basic authentication for Web pages.
See W3C Security Resources for acknowledgement of the limitations of basic authentication. Cookies Cookies are small amounts of text stored and later retrieved by a Web server on a client machine. They allow the server to keep track of the browsers activities, and connect individual Web requests into something like a session, otherwise impossible on the Web, which is 'stateless'. For example they can be used to provide customization features or target advertising better. They can also be used to prevent the user having to be authorized for every password protected page they try to access during a 'session', by recording that they have successfully supplied username and password already.