From http://www.w3schools.com (Copyright Refsnes Data)

CSS background-position Property

Example

How to position a background-image:

body
{
background-image:url('smiley.gif');
background-repeat:no-repeat;
background-attachment:fixed;
background-position:center;
}

The background-position property sets the starting position of a background image.

Note: For this to work in Firefox and Opera, the background-attachment property must be set to "fixed".

Default value:	0% 0%
Inherited:	no
Version:	CSS1
JavaScript syntax:	object.style.backgroundPosition="center"

The background-position property is supported in all major browsers.

Note: No versions of Internet Explorer (including IE8) support the property value "inherit".

Value	Description
top left top center top right center left center center center right bottom left bottom center bottom right	If you only specify one keyword, the second value will be "center". Default value is: 0% 0%
x% y%	The first value is the horizontal position and the second value is the vertical. The top left corner is 0% 0%. The right bottom corner is 100% 100%. If you only specify one value, the other value will be 50%.
xpos ypos	The first value is the horizontal position and the second value is the vertical. The top left corner is 0 0. Units can be pixels (0px 0px) or any other CSS units. If you only specify one value, the other value will be 50%. You can mix % and positions
inherit	Specifies that the setting of the background-position property should be inherited from the parent element

How to place a background image
This example demonstrates how to place a background-image on the page.

How to position a background image using %
This example demonstrates how to position an image on the page using percent.

How to position a background image using pixels
This example demonstrates how to position an image on the page using pixels.