Apple's iOS 9 update now makes it possible to install an ad blocker. This isn't system wide, and will not block ads within apps. It's just for the browser. To do this, you'll have to download one of several ad blocker apps that are available in the App Store. Leo uses Crystal. Then you'll see in the settings that you'll be able to enable it.
Les thinks that website advertising is coming to an end. Google is taking more of the pie and ad revenue isn't really there anymore because AdSense has changed. He isn't really sure how that is changing, but he needs alternatives to raise more revenue from his website. Leo says one of the reasons that ad revenue is dropping is because usage of AdBlockers is exploding. People don't want ads on their surfing experience because they believe they're being tracked and they don't like the fact that it slows down loading times. It also goes against mobile bandwidth caps.