function switchImages(activeStyle) {
    var i, img;
    for (i = 0; (img = document.getElementsByTagName("img")[i]); i++) {
        if (img.src.indexOf("_lt.") != -1 && activeStyle == "dark")
            img.src = img.src.replace("_lt.", "_bk.");
        else if (img.src.indexOf("_bk.") != -1 && activeStyle == "light")
            img.src = img.src.replace("_bk.", "_lt.");
    }
}