I have 2 monitors -- Firefox always opens on the 2nd monitor -- how do I get it to open on the primary ?

Actually this is a classic Firefox bug. What you do is this.

1. Open Firefox.
2. If opened on wrong matter monitor. Click the maximize button so it is NOT maximized on the second monitor.
3. Drag Firefox to your desired monitor.
4. DO NOT maximize it yet. Just close Firefox.
5. Reload Firefox and it should now open on the monitor you close it on. You can now resume using it maximized.

Here's the thing. Firefox when maximized, for some reason will always open in the monitor it was closed on if it was maximized. This bug drove me nuts a couple years ago and it STILL is there. Maybe its not a bug in Mozilla's perception. Could be intended. But... anyway, that is how you fix it. =)

Honestly, thats the only problem ive ever had with firefox on multi mons. And when this happened to me, it took me a while to find the answer even on a google search. It is so irritating lol.