Automatic Internet Login/keychain


I have a question that may at first seem a bit typical but is a bit more complex. Basically I have ruled out that it is a keychain issue and has more to do with the way my internet service is configured here in Japan. I am logging in on a broadband ISP via ethernet with Tiger (latest version) on a Powerbook G4 (brand new), and the service is apparently set up to only allow a user to log in and stay connected idly for about 3 or 4 hours, after which the connection resets and I have to log in again with my pre-assigned username and password.

This is of course a bit annoying. I don't mind terribly not being able to stay online constantly, but having to log in repeatedly is a hassle. The username and password are not retained in keychain because, it seems, this is not a fillable form but instead a pop-up authentication window in Safari that prompts me for my username and password. Reliably the dialogue reads: "To view this page, you need to log in to area "[ISP Name] (IDXXXX)" on [IP Address." The ID Number changes every single time, but the rest remains constant. I am prompted then to type my username and password.

Is there any way to automate this process, perhaps by making my own html page?