But what I actually meant was a header image. I know how to make a stripe orcolour header full width.
What I am thinking of is this:
Say I have a panorama picture that is 1500 px wide and a 150 px high. Now this look great on a screen that's 1500 px wide but on a 800x600 screen you only see the lefthand side. What is want is that when you see the header on a smaller screen you see the center of the image. So you lose a bit of the left and of the right of the image.