Keep menu & content box same width
===

I would like to get your suggestions on what I should do.  I am trying to keep the navigation bar and the content box on a website I'm working on the exact same width.  I've tried adjusting using both percentages and pixels...but once it looks perfect on my laptop, it does not on a larger monitor or on my cell phone browser.  Any ideas of what I can do? You can view the website at www.shaunmichaelmusic.com/new

Thanks in advance for you help!