I have a dual monitor set-up, with sharing. I am on a Mac OS X Version 10.7.5 I am viewing my Firefox window on my secondary monitor. (NOT Primary) When I click any video to full-screen it loads the full-screen on my primary monitor. When I click the window to full-screen (on my secondary monitor) it fills the primary monitor. Before I upgraded, this morning, I could click the full-screen button and my video would appear on the secondary monitor. (The same monitor.) Before this morning, I could re-size the browser window to full-size and view it in my secondary monitor. (The same monitor!) So, explain to me, why the change? Why is it when I click on a video to enter full-screen, or want to re-size a window to full-screen on my secondary monitor, it views on my primary monitor. Does this make any sense? Why? Why would somebody want to browse on one monitor, want to watch something fullscreen, click a button and then watch it on another monitor? I just don't get it. Or why would someone be browsing in a window on one monitor, click full-screen, and want to browse in the same window on another monitor? I am sitting here facing my secondary monitor (which I use as my art-board) and my primary monitor sits to my left. I mainly work from my secondary monitor, so when I am drawing, painting and designing my cursor doesn't 'run into' my dock features, calendar, ext. When browsing in Firefox my window is where it should be, in-front of me. So why would I want to watch a video or browse the web on my left? Why? Why would any developer or designer do this! Especially considering the second, non viewing screen is black! Which means my secondary monitor (in-front of me) is black. When I click, view full-screen, whether video or resizing windows, whether it is my primary or secondary monitor, don't you think the screen should appear full-screen in the monitor I am using?! Right?! I mean somehow you calculated a way for Firefox to recognize which monitor to reopen in. So what's up? I didn't have this problem last week? So tell me . . . why can't I open a video in full-screen on my secondary monitor like I have been doing for years? Why am I even having to write a complaint about something I used to be able to do. AND NOW I CAN'T. I just checked Safari. Wow. Look at that! When I want to view a video in full-screen in the appropriate monitor I can! Wow! I can actually click on my secondary monitor and it's recognizes I want to watch the video on the same monitor. I used to be able to do this in Firefox. I guess it is time to give up on Firefox. And choose a company who understands user-perspective. Or at-least understands what an upgrade is.