My mail application likes to use a LOT of "real estate" to do its work which leaves only a few lines to display the email text. To get around this I have taken to 1) move the display so that just the text area appears and 2) drag the bottom of the browser to the bottom of my display device.
This used to work great and then someone (a few releases ago but this might not even be firefox (nightly)) changed the behavior to only apply to the tab where I took this action.
I think the action should be applied to all other tabs AND survive a browser restart.