How do I block websites on my iPad

You can set the restrictions for access to Safari all together but not sites, if you want to do that the click on settings then click restrictions then turn Safari off.

Download a browser with parental controls.

Settings-general-restrictions.

It will allow you to broadly filter content.

There is no blacklisting on the iPad itself.

Try this app

SmartWeb: Safe Browsing and Parental Control. And it's quite cheap too.

If you want to keep using Safari then you need a filter that's on the network. You can set this up yourself by installing a filter on your router, or use a web-based service like ProxyGroove.