/* Image style */
#scrollUp {
    background-image: url("img/top.png");
    bottom: 16px;
    right: 16px;
    width: 50px;    /* Width of image */
    height: 50px;   /* Height of image */
}

#scrollUp:hover {
 filter:alpha(opacity=50);
    -moz-opacity: 0.5;
    opacity: 0.5;
}