It looks like some elements use absolute positioning, while others use relative positioning - you will have to choose one or the other. For example your title image (images/logolayer2.png) is always 401 pixels from the left of the browser window, while the blue background behind it (images/top.jpg) doesn't have an absolute position specified. You can add an absolute position for images/top.jpg in style.css, or have it placed inside the same div as images/logolayer2.png .
I'm not an expert with HTML, so I found the easiest way to check positioning was to load your site, then play around with the width of my browser window, and see which elements move around. This is why it's good to work with a huge monitor - just shrink the browser window size, and you've tested for a smaller resolution