Summarize the following:
This will display all of your recent apps, including your Safari window. This will close the current instance of Safari, allowing you to try launching it again. If Safari has completely frozen your iPad, you can use this button combination to force your iPad to shut down and restart. This may take about 10 seconds. The Apple logo indicates that your iPad is restarting. It may take a minute or two for your iPad to boot back up. You'll need to enter your device's passcode after completely resetting. Once you've reset, try opening whatever it was that caused Safari to freeze.

Summary:
Double-tap the Home button to open your recent apps. Swipe up on the Safari tab. Press and hold the Power and Home buttons if your iPad is completely frozen. Continue holding both the Power and Home buttons until you see the Apple logo. Enter your passcode. Try Safari again.