Made some edits to the description of the 5000 pixel move mentioned above. I had previously said it was the width when in fact what I'm doing is positioning the element 5000 pixels off the right side and then bringing it back by using a negative left margin. This in combination with an auto width causes (working) browsers to properly redraw that background element when you need to scroll the page sideways.
Here's the CSS for that top band element:
#topband {
position: relative;
display: block;
width: auto;
height: 235px;
margin-bottom: -235px;
left: 5000px;
margin-left: -5000px;
z-index: -1;
overflow: hidden;
background: #586739 url(../images/topband.jpg) repeat-x 0 0;
}