Normally, tapping the device home button should switch from Firefox to your device's home screen. There is a function to show a search box when you tap ''and slide up'' on the home button, or press ''and hold'' the home button, but that wouldn't usually fire just from a straight tap. If you have a Galaxy S5 that you updated to Android 4.4.4, check out this thread: http://forums.androidcentral.com/samsung-galaxy-s5/490111-home-button-my-s5-google-now.html (8 pages of unhappy customers and various fixes suggested)