We've disabled the popups on purpose in the tests. If you want an easy way to check the pinyin/definition of words there (or anywhere else on the Internet) and use Firefox, you should check out our Firefox plugin.

http://popupchinese.com/words/plugin

Once it's installed, enable it using the right-click menu. Then just put your mouse over any Chinese text for a dictionary popup with english and pinyin. You can also use Control+Shift+A to toggle the plugin on and odd. It's a pretty convenient online reference tool.

Note that it may take a few moments for the link to load when you click on it - our system compiles a custom plugin for everyone. It also integrates with your private wordlist, so if you're using it to read material on other sites, you can send words to your vocab lists simply by typing "A" when the popup is open.