If you have a Java-capable browser (Internet Explorer 4+ or Netscape 4+) and the games screens are blank, you most likely do not have Java and JavaScript enabled on your browser. Follow the instructions for your browser.
Netscape 4+
Internet Explorer 4+
If you've already enabled Java, check to see if your hard drive is full. In order to play you should have at least 1 megabyte of disk space available on your computer.