If you're running Mac OS X 10.3, just launch Safari. Go to
Safari/Preferences, "General" section. There's an option called Default Web
Browser, and next to it, there's a dropdown field. Choose your default
browser in the list, and if it's not listed, click Select and browse your
applications folder till you can find it. This should solve the problem.
Also, your default mail program is set in Apple Mail's Preferences Menu. I
think it was better in Jaguar where the default web applications were
grouped together in the System Preferences. This approach was much more
logical, but I guess Apple just wants you to give their applications a try
before choosing others. Hope this solved your problems.
Kind regards