Double tap the home button and the apps in the multitasking display will appear on the screen. Swipe up and off of the screen on every app preview thumbnail to close each app. After you close each app, go to clear Safari by going to Settings>Safari>Clear History and website data. Tap the home button once. Then reset the iPad by holding down on the sleep and home buttons at the same time for about 10 seconds until the Apple logo appears on the screen.
IF double tapping the home button does not allow you to get to the apps in the multitasking display and the screen remains in the frozen state, perform the reset first, then clear Safari like I described above.