One of the thorns in my side with respect to web design is keeping a site uniform when different people access the site who have different resolutions on their computers. To see what I am talking about, on the following site, http://www.keyfreight.net the site can be viewed at 800x600, 1024x768, and 1152x864 and the yellowish graphic running along the top will expand (or shrink) based upon the resolution of the person hitting the site.

How is this done? I am sure the answer is simple, but it is driving me crazy.