Safari can freeze up. The iPad screen will look greyed out. Clicking on any links will not be possible.
When it happened to me I opened a different browser and looked for a solution. Fortunately, an Apple forum had a very useful post. It works:
Go to Settings–Safari. Clear history, cache, and cookies. Restart iPad (turn off by holding down the Sleep button until Power Off appears on screen and then turn on by holding down on Sleep button until Apple logo appears).