DO NOT CHEAT YOURSELF OUT OF LEARNING - The answers will need to be highlighted to view, I don't want to spoil the fun for everyone.
Resources to learn about XSS:
Below you will find my answers to the six challenges on their site.
In the search form enter:
In your comment enter:
<img src=wizbang onerror='alert(0)' />
in the url bar enter:
In the timer form enter:
Hopefully ill do a formal writeup and really explain why all of the answers work and maybe show some alternative ways to complete the challenges.