There are many discussions on this topic. Right under the words that say your browser is ignoring the applet tag there is a link which is: Scenario not running? If you read what's there and did what it told you and it still doesn't work, then make sure you're using a browser that lets applet tags. Try using Internet Explorer.

Never mind. It turns out that Google Chrome no longer supports the <APPLET> technology. Source: Oracle

I guess you beat me to it :)

It's been like that for a while. For sure before you became a Greenfoot user, which is why I suggested Internet Explorer, since that works for me. Now you did.