When Safari quits like this, it's usually due to a lack of system memory (RAM). Switch the iPad off completely by pressing and holding the Power button until the slider control appears. Now accept the offer to switch off. Wait until the rotating white bezel has disappeared and the screen is completely blank. Now press the Home button until the white Apple logo appears. The iPad will power up. Doing this lets the iPad's operating system reclaim 'lost' system memory and should fix the problem. Apple recommend you switch the iPad off occasionally to enable the operating system to do this and other 'housekeeping' tasks.
Tim