This book support site was hosted by a simple account's web pages since the mid-1990s (1995 or 1996, as far as I can reconstruct). It began its life on a server and domain name run by rmi.net (Rocky Mountain Internet, an early dial-up provider); which was later acquired by MindSpring; which was eventually bought by EarthLink. Along the way, the original www.rmi.net/~lutz URL kept working reasonably well, so there was little incentive to change the domain name or host for a non-commercial resources site whose location was published in some half million books.
And then the reality of today's web struck. On October 24, 2015, the address of one of this site's pages was posted on a high-volume forum (Hacker News is a prime suspect), attracting over 10,000 visitors to the page in a day and a half. Traffic is a great problem to have, but this caused the site to exceed its archaic bandwidth quota and be shut down completely for an entire week, denying access to an untold number of readers. EarthLink proved characteristically inflexible on the issue (they've also changed URL structure and other service components in the past, with neither notice nor recourse).
Consequently, after two decades, the site has finally been moved to a GoDaddy web hosting account and server as of October 26, 2015, using a custom registered domain name for its new URL: learning-python.com. The new URL should prove more stable, and the new unlimited-bandwidth host will accommodate both higher traffic rates, and new functionality in the future, including Python-coded server-side interaction scripts. The prior site's location will maintain redirection pages until its traffic fades.
I regret any confusion the move may cause, and the books site resisted a commercially based presence as long as it could; but working at a different URL beats not working at all. The new scheme will hopefully weather the years as well as the former—though the Internet seems likely to be as different two decades hence as it was two decades ago. All of which might embed a lesson for prudent readers about becoming overly dependent on web-based companies in general. Today's cloud providers and social media sites, for example, could very well be tomorrow's multiply acquired ghost companies.
Update: site MIA, April 2019: EarthLink took down personal-webspace sites, including the redirection pages described above, for at least a month this year without notice. The redirection pages were eventually restored, but this company's service for paid accounts seems fleeting and tenuous at best. Hopefully, readers of older books today will find the new site with a search if—really, when—EarthLink pulls the plug on the old URLs for good. Alas, global conversations last only as long as profit-eager companies are willing to keep the venues open.
Farewell rmi.net, March 2020: it's official—EarthLink will be permanently deleting all personal-webspace sites it hosts as of March, 2020. Naturally, a monthly-fee reduction isn't part of the change. Among the condemned are the forwarding pages at the old rmi.net/~lutz books site, which will have been online for 24 years by the time the lights finally go out next year. Read the late April 2019 announcement here and here; see you at learning-python.com; and rest in peace (or at least in embarrassing web archives from the 90s), rmi.net.
Epilogue, July 2020: the rmi.net forwarding site was still up as of mid-May 2020, despite the fact that everything on Earthlink still said it would cease to be in March. The cause of the delay was unknown, though the year's global crises may have stayed the execution. In any event, rumors of the site's demise were not exaggerated: as of July 2020, it responds no more.
In the interest of fairness and closure, it's worth adding that GoDaddy also became unusably slow in 2020, forcing this site to move yet again—this time to an Amazon Lightsail VPS (more words here). Takeaway: brands crumble, marketing promises are broken, and being skeptical of online services just makes sense.