Great site design! I love that lil cartoon you got.
The site utilizes ajax real nicely...the timer sounds are a nice add too.
I see one design aspect I would improve upon. The links at the bottom look generic using the default blue and underline. Maybe css that some to fit the site color scheme or something.
The CSS is valid, however the xhtml is not. The xhtml has a few errors: [Invalid] Markup Validation of http://www.powerhower.com/ - W3C Markup Validator