Sorry that you feel your issue is with Firefox, but it's not possible to specifically contact someone who works for Mozilla, the organization that created the Firefox web browser and maintains it.

Firefox 52 is very old and hasn't been supported in a long time.
Perhaps Yahoo made some changes and older versions of Firefox just don't work now. I have have had that happen with a few websites recently where the sites was updated, and a newer version of Firefox works well on those websites. I have old and new Firefox versions installed, and some in between.

Try clearing your cache and see if that helps.

Even after I wasted the memory to "refresh" Firefox, which logged me out of everything and now nothing's letting me back in...Yahoo is opening a temporary backup account but not opening my main business e-mail account, which of course has everything I go online to read in it. Obviously Yahoo is trying to sell paid e-mail by disrupting people's free e-mail service, which ought to be illegal and certainly won't work with me...but I thought it might be worth asking whether there WAS a way to fix the problem in Firefox. If Mozilla's not maintaining Firefox, then ever using it at all has not been a good idea.

Sorry, but I didn't advise you to do a Refresh of Firefox.

Mozilla is maintaining Firefox, you happen to be using an version of Windows which precludes you being able to use the latest Firefox 77 version (you're 25 versions behind the latest version of Firefox).

Firefox (and this website) "reads" the browser that you used here as using Windows Vista, which neither Microsoft or Mozilla has support for quite awhile. And if you happen to be using a newer version of Windows like Win7, you probably have Firefox set to "compatibility mode" so that websites you visit "think" that you are using Windows Vista. You can right-click your Firefox desktop shortcut and open Properties; then view the Compatibility tab to view that information and disable it.

but I thought it might be worth asking whether there WAS a way to fix the problem in Firefox. If Mozilla's not maintaining Firefox, then ever using it at all has not been a good idea.

Support for the old Firefox 52 ESR was made End of Life or EOL as of June 26, 2018 with no more security/stability updates since.

Firefox Releases since the Firefox 52 Release has required Windows 7, 8 (8.1), 10 to run since. https://www.mozilla.org/firefox/52.9.0/system-requirements/ https://www.mozilla.org/firefox/53.0/system-requirements/ https://www.mozilla.org/firefox/77.0.1/system-requirements/ (current Release)

https://www.mozilla.org/firefox/releases/

Other web browsers like Chromium/Chrome for example dropped support of Windows Vista along with Windows XP, and Mac OS X 10.6, 10.7, and 10.8 back in April 2016. So Mozilla supported WinXP and Vista for over two years longer.

If you want to use more current version of Firefox (and other browsers) you need a more current OS. Besides using Windows 7 or newer your system may be able to handle dual booting with a Linux distro with a lighter desktop environment like XFCE. One of the PC's I have is dual booting 32-bit Vista and 64-bit openSUSE 15.1 (using XFCE) on a 12yo Intel dual-core (64-bit CPU) system with 4GB RAM running fine.

Unless of course you are indeed using Windows 7 or newer then you may have altered the useragent. https://support.mozilla.org/en-US/kb/websites-say-firefox-outdated-or-incompatible

Or you may be for some reason running Firefox in compatibility mode as if you have Windows Vista. https://www.howtogeek.com/howto/windows-vista/using-windows-vista-compatibility-mode/

This will allow you to download and use current Firefox and for websites to know you have current Firefox.

If you are indeed using Windows Vista then this post does not apply.

Thanks, all...You're not the ones who need to hear this, and it sounds as if the ones who need to hear it are deliberately not listening, but I don't like to support built-in obsolescence. The device I have is the device I have. I've not cluttered its memory with any "updates" that could be avoided. If you want me to use anything online, you want to avoid any and all changes that affect the way I use it, including changes that eat up my browser memory. So, an answer that solves my problem would come from Firefox and would involve the company's fixing THEIR problem. "Get a new [anything]" is a non-solution; it basically tells me, if and when I do get a new laptop, don't clutter it with Firefox.

Yahoo's allowing problems to arise and trying to steer people to paid e-mail. Isn't that hilarious?! Companies investing actual money in the fantasy that, if people haven't become OBSCENELY RICH using their free service, those people are going to feel so dependent on their service we're going to buy anything from them?

If continued use of free stuff starts to cost us money, or time, or even browser memory...that's when we say "You can keep it."