/* Grid */
#grid{

    /* Vertical grid lines */
    background: url(../img/bg-grid-960.png) repeat-y 0 0;

    /* Dimensions - same width as your grid with gutters */
    width: 1020px;

    /* Grid (left-aligned)
    position: absolute;
    top: 0;
    left: 0;
    */

    /* Grid (centered) */
    position: absolute;
    top: 0;
    left: 50%;
    margin-left: -510px;

}

/**
 * Horizontal grid lines, defined by your base line height
 *
 * Remember, the CSS properties that define the box model:
 * visible height = height + borders + margins + padding
 */
#grid .horiz{

    /* 20px line height */
    height: 19px;
    border-bottom: 1px dotted #aaa;
    margin: 0;
    padding: 0;

}