function swapImage(_which, _id) {
    document.getElementById(_id).src = _which;
    //alert(captionInner)
}

var preFetchImage = new Image();
preFetchImage.src = "/images/hm_ss_solar_on.jpg";
preFetchImage.src = "/images/hm_ss_road.jpg";
preFetchImage.src = "/images/hm_ss_dude.jpg";
preFetchImage.src = "/images/hm_ss_skyview.jpg";

function swapBackgroundImage(_which, _id) {
    //alert(document.getElementById(_id));
    document.getElementById(_id).style.backgroundImage = _which;
}