How To Open Firefox Without Reopening Tabs
The Short Answer: Right-click the Firefox icon in your Windows task bar and select the "Open new window" task.
Longer Version
I sometimes wonder why I still bother with Firefox. It crashes and freezes more often than Chrome, and is more prone to JavaScript attacks. Being committed to products that don't have the backing of a giant software company has its drawbacks. But I am committed. Because I believe in open-source software, and I don't want Google to have the benefits of a browser monopoly.
Today, I clicked a link in my Google search results, to see information about a band I'd never heard of, and was presented with a phony "Critical Error" page, along with an endlessly growing stack of JavaScript dialogs. Firefox itself offered me no way out, so I had to use the Task Manager's "End Task" feature to kill Firefox. I then reopened Firefox... and it reloaded the tab I had just opened, and I was one again presented with the same problem.
I wondered whether Firefox might have a command-line option that would prevent it from reopening the tabs I had open when the application was closed. Or maybe I needed to use Firefox Safe Mode? That didn't make sense -- I wasn't interesting in disabling add-ons. I did a bit of searching, and the answer didn't come to hand as quickly as I thought it would. Most posts suggested changing my Firefox settings... but I couldn't change the settings while the application was strangling itself. Then I came across this simple answer mentioned above. Much better!
Bonus! "New Private Window" Task
I also discovered that Firefox has a "New private window" task that you can access by right-clicking the Firefox icon in the Windows task bar. This is similar to the "Incognito" feature on Chrome, which is very handy for testing a website as a newcomer, sans cookies.