Let's say I'm using Firefox and I get a kernel panic, which just happened again. After I restart the Mac, I restart Firefox, which immediately tries to the page that caused the kernel panic -- thus causing another kernel panic ad infinitum. How do I break this cycle?

In the past when I restarted Firefox I frantically try to close windows and tabs and quit of force-quit Firefox, using my mouse buttons and command-W and command-Q. If I'm fast enough, I can keep Firefox from reloading the troublesome sites, but often it takes a couple attempts, and it's such a dumb, tedious way to solve the problem. I also have multiple tabs open at once whenever I'm on the internet, so I'm not always certain which tab, i.e. web site, is causing the kernel panic. When I figure it out, I make a mental note, which is now turning into a text document with a list of web sites I can't visit. Some of these web sites had been useful.

Quite frustrating, really. One of the few drawbacks of using an old system.

This is Firefox 39.0.3, but it happened to earlier versions the past few years. Years ago, I'd never even seen a kernel panic. My research from previous kernel panics suggest that there's something wrong with my imac's graphics drivers, something about how they interact with web sites via Firefox.

I can't fix that, but does anyone have any idea how to keep Firefox from reloading past pages as soon as it restarts? In fact, in the Prefs, I even have "clear history after quitting Firefox" selected but it doesn't work in this circumstance. There should be an option "after a Mac crash, do not load previous session." This is a fairly serious problem.

In FF 46.0.1, there is a preference that might help, if you have the same preference options. Go to Firefox > Preference > General and look at When Firefox Starts. If you set that to either show your home page (assuming that it's not the one that causes the problem) or show a blank page, that should do it. One of the options in my version is to do exactly what you don't want, namely show windows and tabs from the previous session.

Jon is right. Firefox's general preferences haven't really changed in many versions. I'm using 41.0.2 and running Lion OS X 10.7.5.
Go to general preferences (immediately you start Firefox, so that you "sidestep" the cycle you describe); select show home page, choosing some such (eg, weather forecast) which is innocuous, and you should be home free.

I'm curious to see if Jon's suggestion is deniro's answer, because apps don't always react as if they've been quit after they've been closed other than by having been quit.

I'm basing that on vast experience with iTunes.

I always have it set to show a blank page "When Firefox Starts." I don't think that's the problem, but I'll try messing with it.

When Firefox restarts after a Mac crash, it doesn't start up with a blank page as indicated by my prefs. It starts up trying to reload the previous sessions, which I do not have checked (i.e. "Show My Windows and Tabs from last time").

That's what I thought you might say. (It's been a long time, but I think restoration of pre-KP states is SOP in OS X.)

The only thing I can think of is for you to figure out where Firefox stores its history and clear that file before you reopen it.

Edit: where does FF store history on hard disk? (/Users/artie/Library/Application Support/Firefox/Profiles/t5wb6yrg.default/places.sqlite [...your specifics, of course.])

From Mozilla's description of the file it's got something to do with bookmarks as well as history, so you may want to save it to your desktop rather than trash it. (I do see a file labeled "bookmarks.html", so I dunno.)

Thanks for the responses. I agree that I need to find the history file. In the past, I haven't found a solution via preferences and other fiddling. It only became a issue problem when kernel panics increased. Years ago that never happened.

You might look to a utility, like OnyX, that can trash browser caches and history without touching bookmarks?

Here's an obvious idea that worked.

Disconnect the modem when you restart the computer. Then when Firefox starts up and tries to load the previous web pages, it will be unable to. Then you can delete the history or do whatever you want.