The real museum and archive types all prefer some kind of analog format to truly save materials. Acid-free paper, some kinds of color prints, Kodachrome (!), are all good.

I do some work on the sound side, and while digital is the way everything's recorded, edited, and published those who want to really archive a recording use analog tape, as wide as possible for minimum noise. A well-produced analog tape on the right material can still be played many years later (how do you think a lot of those "classic" albums from the 1950s/60s were re-mastered to CD?). There's still a small business in (re)building analog tape machines for the archival as well as the snob and old-techies markets. Of course, for most brands it's like fixing a steam engine -- if you need parts you must find another machine to scrap or get really good at precision machining and plastics stuff and designing and building electronics. Digital tapes and magnetic discs "fade" over time and must be re-written on a regular schedule to maintain the data -- is Joe Home Recordist doing to do that? Optical discs (CDs, DVDs, etc.) are supposed to last nearly forever, but there have been enough failures that such claims are treated with much salt and multiple copies. The issue of whether the right hardware and software will be available at some indefinite future date is also a real one. How many of you have a computer that could use a 8" floppy disk? Even if you could find and connect a working drive, what physical and software formats did that desk-size word processor use?

With analog, there's a physical representation of the picture, sound, etc. on the paper, film, tape, or plastic disk that can be read by a human or scaled up in some way to be understandable. That's why a Real Record was sent on Voyager. So when you scan your slides don't throw them away afterward - you (or somebody) will probably need them again someday. Of course, if (as with many of mine) your Ektachrome has turned green or faded out or your Agfachrome gone orangey you may be out of luck; with Kodachrome gone, what's truly archival any more?

For this Board, something like the Wayback Machine might be a good interim solution. Take a picture of the site, then give it to somebody that will save it on another server that's generally accessible and professionally maintained. Good as long as THEIR money holds out ...