CSS 3 Syntax Property Values

left top
left center
left bottom
right top
right center
right bottom
center top
center center
center bottom

http://www.w3schools.com/cssref/playit.asp?filename=playcss_background-position&preval=50%25%2050%25

body {
    background-image: url('smiley.gif');
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-position: 30% 20%;
}