I was reminded of this recently by some feedback that came in regarding one of the web sites we maintain; the 'online edition' of the first 50 years or so of the British Colonist newspaper. The substance of which was "The search term highlighting doesn't work anymore, and I can't print sections of the pages - what gives? Please make it work like it did before."
Now, work on this particular project proceeds in fits and starts. It just happens that lately we've been doing a major overhaul, but none of that work has yet been released in the wild. The site that is available to the public hasn't changed in years.
So why did things suddenly stop working? The answer is they didn't, not at our end. The site still does everything it did before. However, I don't discount the feedback, because it highlights a weakness of the original site design: much of its functionality depends on proprietary features available in Adobe's Acrobat PDF viewer. And while Acrobat was nearly universal a few years ago, it is much less so now.
If I had to hazard a guess, I would say it's likely the user either changed web browsers recently, or is using Firefox and upgraded it to a fairly recent version. Recent versions of Firefox no longer use Acrobat to display PDFs, at least not out of the box. I don't believe the Firefox reader has the ability to print sections of PDFs the way Adobe does, and it doesn't do search term highlighting either, at least not the same way.
Web sites are in fact a bit like organisms; they depend for their existence on a whole ecosystem of supporting technologies. And when the ecosystem changes (and it does, constantly), the same evolutionary rule applies: adapt or die. That's why web sites can't really be done as one-shot projects; a certain amount of care and feeding is required, in perpetuity, if you want them to last.
So in order for the site to stay the same, we have to change it. As mentioned above we are in the process of rebuilding the Colonist site, which will launch sometime before the end of this year if all goes as planned. In addition to 10 more years of content, it will incorporate an improved document reader that will no longer depend on Acrobat so much. Search term highlighting will work much better across a much wider range of browsers, and users will see the whole issue at once, rather than viewing a page at a time.
We haven't completely done away with the need for Acrobat or something similar though: users will still need to download the PDF if they want to print sections of the page, since our online reader doesn't have that capability. Still, I think our new approach is more than one step in the right direction, and will hopefully do the trick until we have to rebuild the site again five years from now.