TimesUpKidz limits how much time your kids' spend on the computer, regardless of activity. It does NOT block specific website, games, or applications. But do not worry. There is a better solution.
If you want to block specific websites, a really good option is OpenDNS. They have a free option that blocks most porn. For a fee, they offer a more sophisticated plan that can block other types of content. The benefit of OpenDNS is that it works across ALL the devices in your house - computers, iPads, iPhones, etc. - as long as those devices are accessing the internet through Wifi or your home router. If your kids are accessing the internet through your cellular data plan, you can investigate the parental controls and web filters built into the iPhone, iPad, and other devices.