Positioned on the background css code example

Example 1: move css background image

background-image: url('w3css.gif');
 background-repeat: no-repeat;
 background-attachment: fixed;
 background-position: center;

Example 2: css image background center horizontally in div

/*
div with 
class="slot_image" 
*/
.slot_image{
    background: url(url) no-repeat center;
}