screen resolution issues for new website

I've completed work on the website for Cincinnati Mindpeace. However, my client is complaining that the site does not look good on (1400 x 1050) screen resolution. I originally designed it to look good for 1024 X 800, but she complained that it didn't look good on 800 X 600. I am new to this game, so I am not sure if it is possible to change the style sheet so that the website will look good on all screen resolutions.
Here is the site:
Cincinnati Mindpeace Website
Many thanks to Eric and all the experts here.

One thing you can try to do is to center the content by surrounding it with a div
<div style="text-align:center">
CONTENT
</div>

Or use percentages instead of hardcoded widths..eg use 95% instead of 650px
See if that helps
Eric