I've never noticed this before. Is there an example page online that works like this?

Right now, every example I can think of is behind an authenticated site. I haven't seen _CTm= documented, but it works on every computer browser I've tried it on. The only 2 parameters I've ever user are xml and xls--but I'm guessing there are more. In my experience, it *is* case sensitive--and the underscore is meaningful.

I can think of a few different possibilities here:

• The server sends plain, unstyled XML, but Firefox 25 changed how it displays unstyled XML
• The server sends XML with a reference to a style sheet, but Firefox 25 isn't retrieving/applying the XSL for some reason
• The server sends XML and a client-side script that normally generates a tree was broken by the upgrade
• An extension that was prettifying the XML became disabled during the upgrade (or Firefox reset during the upgrade, removing all extensions)

Do any of those appear relevant?

In your "More System Details" screen, one of your plugins is listed under the name NOTFOUND. Can you track that down and see what it is? If it's not obvious from the Add-ons page, maybe this script will help (scroll down for plugin details): https://jeffersonscher.com/res/jstest.php.

Well, I was really hoping that someone on this forum would help me find the actual documentation on this feature that works with the major browsers. My tries with Google turn up too much junk. In any case creating a new profile caused both the new profile and my default profile to start working OK--so apparently some malware corrupted something. Some time when I don't have anything else to do I'll create a public page that uses this feature because it is really cool. I'll mark your response as helpful but leave it out here at least a week in case someone can actually show where it's documented.

Thanks!