I installed Firefox on a new computer with Windows 10, and initially was unable to get into full screen (F11). After some experimentation, I came up with a procedure that works, but involves starting Firefox twice every time - a minor nuisance. I have 1 "Pinned" Tab plus other open tabs with full screen working, and shut down Firefox normally (I don't get the expected warning about closing multiple tabs). The following steps get Firefox back up and into full screen mode:

1. Start Firefox. This gives a maximized blank page with address bar and tab bar with a single tab. 2. Press F11. Oddly, instead of putting it in full screen mode, it changes the page to "Restored" size. 3. Maximize. Window expands to its appearance after step 1. 4. Shutdown Firefox. Window goes away. 5. Start Firefox a 2nd time. This time it will come up with the Firefox "Restore" page (with address & tab bars) that shows the tabs that were open at the earlier shutdown, and gives the opportunity to select which tabs you want to come up this time. At this point F11 will toggle in & out of full screen properly, so steps 6 & 7 can be in either order. 6. Press F11. It will go to full screen (i.e. address & tab bars disappear). 7. Click the "Restore" button. Tabs from previous shutdown are restored and F11 is fully functional. Questions: 1. Why don't i get the warning for closing multiple tabs? (It no longer appears to be an option.) 2. Since (under XP at at least) the "Restore" page should only appear following a forced or abnormal shutdown, why is it even getting involved? (Both of the shutdowns mentioned were normal.) 3. Why doesn't Firefox come up normal the first time, with only the tab(s) that were pinned, and with F11 functional?