Three things to do after installing Firefox 54
First, disable the menu that is shown by pressing the Alt key. Open a new tab, type in “about:config”, search for “ui.key.menuAccessKeyFocuses” and set this configuration to “false”.
Second, on the same configuration page, search for “layers.acceleration.force-enabled” and set this value to “true” in order improve the performance of Firefox by using hardware acceleration.
Third, set “browser.tabs.closeWindowWithLastTab” to “false” to prevent Firefox from closing when you close the last tab.