HTML background image offset by x pixels from the center

Question

I\'d like to put an image as the background of a webpage but have it offset by some number of pixels with respect to the center.

How can I do this?

I want:

Answer 1

Nice answer Luke,

one more thing, if your block width is larger than screen resolution, your must put your block in another container and do this:

#container{
  position:relative;
  overflow:hidden;
}

#shadowBox{
  width: 100%;
  left: -100px; /* this must be TWICE the required offset distance*/
  padding-right: 100px; /* must be the same amount as above */
  background-image: url("background-image.png");
  background-position: center;
  background-repeat: no-repeat;
  position:absolute: /*this is needed*/
}