Design for different browser size

Hi

I just want to say first of all, thanks to all those who offer help on these forums. Where would people like me be without your help

I have designed my website http://www.thebreadcrumbtrail.org to the best of my abilities in Firefox in the current browser size I use. I’ve tried to fit all my website content into a width of 1,028px, which is the width of my header image.

I went to http://whatsmy.browsersize.com/, maximised my broswer window and my browser size is:

Browser window width: 1024
Browser window height: 550

Which doesn’t make much sense to me seeing as that is a measurement of the entire browser right. If I look at my homepage, my header image isn’t the full width of the screen, yet at 1028, it is wider than the supposed max width of the screen???

Anyways, as I zoom in and zoom out from my current view, everything moves, and gets really ugly. How can I fix things like the post background, and searchbar in place?

Thanks in advance

James