The Media tab only displays when actual media are found, which you can check by viewing a text-only page. Changes are (and I’m not sure) some optimizations have been applied in recent Firefox versions. For instance, the Activate plugins section in the Permissions panel is left out if the Flash plugin is not set to "Ask to activate" or "Always activate". This may be related, or an intended result of that change.

Therefor I assume there is something wrong (as in "undetected") with regard to any media when building the page. Would that be possible?

The webpage is actually the homepage for one of my one-man businesses, and it has plenty of graphics. I think that the Firefox internal code for page info has changed in the lat year or two because I don't remember this problem before that. I code in raw HTML and CSS with a bit of java thrown in. I think I have just resolved the problem in terms of finding a workaround.

I have a rather complex naming structure for the 4 small websites I've written, where only one primary domain exists, and the other domain names (to save money on hosting) are "aliases" of subdomains of the primary one. For example, if abcd.com is the primary domain, then efgh.com is an alias for subdomain efgh.abcd.com, which is structurally abcd.com/efgh/.

If I try to get page info for efgh.com/index.htm, I see no Media tab, but if I get page info for efgh.abcd.com/index.htm or abcd.com/efgh/index.htm, then I DO get the Media tab.

Problem (sort of) solved via a workaround.