David's 2010 MacBook Pro has OS X 10.6.8 and some sites don't support older versions of Safari on Snow Leopard. Leo says that David may need to upgrade his OS. But the question is, can he? The latest update says you can't update to Sierra unless he has 10.7 or later. So he needs Lion. He can't upgrade straight to the latest version. So search the app store for OS X Lion. Here's where - https://itunes.apple.com/us/app/os-x-el-capitan/id1147835434?mt=12.
Find out how to upgrade here - http://www.apple.com/macos/how-to-upgrade/