I placed my favicon here:
http://www.vittoriosastarsnursery.com/favicon.ico
But for some reason it doesn't want to show in Firefox. It did work in IE, but I'm more concerned about getting it working in Firefox.
I can see it in Chrome, Firefox, and IE. My friend had a problem like this when we were testing back in college. It was just a weird caching thing that made her think it wasn't working right. I'm sure that everyone besides you will be able to see that it works fine.
Try opening the Dev Tools (CMD + Option + i on Mac) and hard refresh the page (hold the refresh button until options appear).
You could always try restarting your browser after clearing the cache and see if that helps.