This might be a good time for you to learn how to use jsFiddle. It's a wonderful free site where you can play around with HTML, CSS, and JavaScript to test your code and deepen your knowledge.

Please consider bookmarking the site now.

When something about JavaScript puzzles me, I always go straight to jsFiddle to experiment. I used it to test many of the code examples I give in the book.

At some point during this course, you're probably going to question the judgment of my answer-checker. Or you're going to come up with some valid code that differs from the code the answer-checker is insisting on. That's the time to head on over to jsFiddle and take your code for a test drive. You can even save your code in a unique URL that jsFiddle generates for you.

I've created a very brief introduction to jsFiddle at jsFiddle that demonstrates how to use the site to test JavaScript.